KIEV (Reuters) - Protests in eastern Ukraine in which pro-Russian activists seized public buildings in three cities are part of a plan to destabilize Ukraine and bring in Russian troops, Prime Minister Arseny Yatseniuk said on Monday. 
 
 Saying Russian troops were within a 30 km (19 mile) zone from the Ukrainian border, Yatseniuk told a government meeting: “An anti-Ukrainian plan is being put into operation ... under which foreign troops will cross the border and seize the territory of the country. 
 
 “We will not allow this,” he said. 
 
 Pro-Russian protesters in the east seized official buildings in three cities - Kharkiv, Luhansk and Donetsk - on Sunday night, demanding that referendums be held on whether to join Russia. 
 
 A similar move preceded a Russia-backed takeover of Crimea in March followed by annexation of the peninsula by Russia. 
 
 Interior Minister Arsen Avakov said on Monday the main regional administration building in Kharkiv had been cleared of “separatists”. 
 
 But police said protesters occupying the state security building in Luhansk had seized weapons and highway police had closed off roads into the city. 
 
 “Unknown people who are in the building have broken into the building’s arsenal and have seized weapons,” a police statement said. Nine people had been hurt in the disturbances in Luhansk. 
 
 Mainly Russian-speaking eastern Ukraine has seen a sharp rise in tension since Moscow-backed Ukrainian President Viktor Yanukovich’s overthrow in February and the advent of an interim government in Kiev that wants closer ties with Europe. 
 
 Russia has branded the new leadership in Kiev illegitimate and has annexed Ukraine’s Crimea region, citing threats to its Russian-speaking majority - a move that caused the biggest standoff between Moscow and the West since the end of the Cold War. 
 
 YANUKOVICH CALL 
 
 The protesters appeared to be responding in part to Yanukovich, who fled to Russia after he was ousted and who on March 28 issued a public call for each of Ukraine’s regions to hold a referendum on its status inside the country. 
 
 A pro-Russian protester stands inside the seized regional administrative building in Kharkiv April 6, 2014. REUTERS/Stringer 
 
 Separately, Ukraine’s defense ministry said a Russian marine had shot and killed a Ukrainian naval officer in Crimea on Sunday night. 
 
 The 33-year-old officer, who was preparing to leave Crimea, was shot twice in officers’ quarters in the locality of Novofedorovka. It was not clear why the Russian marine had opened fire. 
 
 Yatseniuk said that though much of the unrest had died down in eastern Ukraine in the past month there remained about 1,500 “radicals” in each region who spoke with “clear Russian accents” and whose activity was being coordinated through foreign intelligence services. 
 
 But he said Ukrainian authorities had drawn up a plan to handle the crisis. 
 
 “We have a clear action plan,” he said, adding that senior officials would head to the towns concerned. 
 
 Avakov on Sunday accused Russian President Vladimir Putin of orchestrating the “separatist disorder” and promised that disturbances would be brought under control without violence. 
 
 Russia has been pushing internationally a plan proposing the “federalization” of Ukraine in which regions of the country of 46 million would have broad powers of autonomy. 
 
 Slideshow (9 Images) 
 
 Ukraine, while drawing up its own blueprint of constitutional changes for ‘de-centralization’ in which smaller municipalities would be able to develop their own areas by retaining a portion of state taxes raised, says the Russian plan is aimed at breaking up the country. 
 
 Referring to the Russian plan, Yatseniuk said: “It is an attempt to destroy Ukrainian statehood, a script which has been written in the Russian Federation, the aim of which is to divide and destroy Ukraine and turn part of Ukraine into a slave territory under the dictatorship of Russia,” he said. 
 
 “This is not going to happen,” he said. 
 
 “I appeal to the people and the elites of the east. Our common responsibility is to preserve the country and I am sure that no-one wants to be under a neighboring country. We have our country. Let’s keep it,” he said. ||||| KIEV, Ukraine (AP) — Pro-Russian separatists who seized a provincial administration building in the eastern Ukrainian city of Donetsk on Monday proclaimed the region an independent republic in a move echoing the run-up to Russia's annexation of Crimea. 
 
 Pro-Russian activists with Russian national flags storm the Ukrainian regional office of the Security Service in Luhansk, Ukraine, Sunday, April 6, 2014. In Luhansk, 30 kilometers (20 miles) west of the... (Associated Press) 
 
 The Interfax news agency said the activists demanded that a referendum be held no later than May 11 on the breaking away of the Donetsk region, which borders Russia. 
 
 In footage uploaded to the Internet, an unidentified pro-Russia activist in the provincial government headquarters in Donetsk asked Russian President Vladimir Putin to send peacekeeping troops to the region. 
 
 "Without your support, without the support of Russia, it will be hard for us to resist the Kiev junta on our own," he said, referring to the interim authorities that took power after the overthrow of Moscow-backed President Viktor Yanukovych in February. 
 
 Ukrainian Prime Minister Arseniy Yatsenyuk earlier in the day accused Russia of being behind the unrest that broke out in the country's eastern provinces Sunday and of seeking to sow instability as a pretext for dispatching troops across the border. 
 
 "The plan is to destabilize the situation, the plan is for foreign troops to cross the border and seize the country's territory, which we will not allow," he said, adding that people engaged in the unrest have distinct Russian accents. 
 
 Yatsenyuk said Russian troops remain stationed within 30 kilometers (19 miles) of the frontier. 
 
 Eastern Ukraine was the heartland of support for Yanukovych, who fled to Russia in February after months of protests. About half of the region's residents are ethnic Russians, many of whom believe Ukraine's acting authorities are Ukrainian nationalists who will oppress Russians. Ukraine's interim authorities deny they are infringing the rights of the ethnic Russian population. 
 
 Since Crimea held a secession referendum and then was annexed by Russia in March, calls for similar votes in Ukraine's east have emerged. ||||| A cordon of Interior Ministry personnel (front) stand guard in front of a group of pro-Russian protesters outside the regional administration building in Kharkiv, April 8, 2014. 
 
 KIEV/DONETSK, Ukraine Police detained 70 people occupying a regional administration building in eastern Ukraine overnight, but pro-Moscow protesters held out in a standoff in two other cities in what Kiev called a Russian-led plan to dismember the country. 
 
 Kiev says the seizure of public buildings in eastern Ukraine's mainly Russian-speaking industrial heartland on Sunday night is a replay of events in Crimea, the Black Sea peninsula Moscow annexed last month. 
 
 Ukrainian authorities gave few details of the "anti-terrorist" operation that cleared the building in the town of Kharkiv but said two police had been wounded by a grenade that was thrown. Russia has denied Ukrainian charges of involvement but warned Kiev against any use of force against Russian-speakers. 
 
 Ukrainian special forces in combat gear, helmets and balaclavas and carrying kalashnikovs and machine guns stood guard early on Tuesday outside the building whose outside windows were broken. 
 
 A partly destroyed sign near the main door read: "Avakov - to jail", a reference to Ukrainian Interior Minister Arsen Avakov. 
 
 The pro-Russian protesters who also took over official buildings in Luhansk and Donetsk demanded that referendums be held on whether to join Russia like the one that preceded Moscow's annexation of Crimea. 
 
 "An anti-Ukrainian plan is being put into operation ... under which foreign troops will cross the border and seize the territory of the country," Prime Minister Arseny Yatseniuk said in public remarks to his cabinet. "We will not allow this." 
 
 Interior Minister Avakov said on Tuesday about 70 "separatists" had been detained in Kharkiv. 
 
 "An anti-terrorist operation has been launched. The city center is blocked along with metro stations. Do not worry. Once we finish, we will open them again," he wrote on his Facebook page. 
 
 Ukraine's Interior Ministry was quoted by Interfax-Ukraine news agency as saying those detained were suspected of "illegal activity related to separatism, the organization of mass disorder, damage to human health" and breaking other laws. 
 
 Russia's Itar-Tass news agency quoted Ukrainian Deputy Prime Minister Vitaly Yarema as saying there would be no storming of Donetsk's regional authority building on Tuesday. 
 
 He said the decision was made after talks in Donetsk with the protesters involving influential and wealthy businessman Rinat Akhmetov, who is from the city. 
 
 On Tuesday about 200 people were gathered in front of the building and a group of National Guard were stood to one side. But the situation was calm and there was no sign of any attempt to enter by force. 
 
 Acting President Oleksander Turchinov, in a televised address to the nation, said Moscow was attempting to repeat "the Crimea scenario". He added that "anti-terrorist measures" would be deployed against those who had taken up arms. 
 
 U.S. Secretary of State John Kerry told Russian Foreign Minister Sergei Lavrov in a phone call that Washington was watching events in eastern Ukraine with great concern and any further moves by Moscow to destabilize Ukraine would "incur further costs for Russia". 
 
 Kerry "called on Russia to publicly disavow the activities of separatists, saboteurs and provocateurs" in Ukraine, the State Department said. The two discussed convening direct talks in the next 10 days between Ukraine, Russia, the United States and the European Union to defuse tensions. 
 
 WHITE HOUSE WARNING 
 
 The White House warned Russian President Vladimir Putin against moving "overtly or covertly" into eastern Ukraine and said there was strong evidence that pro-Russian demonstrators in the region were being paid. 
 
 Lavrov told Kerry that constitutional reform was required to resolve the crisis. Russia says this would give Ukraine's regions more powers, as it believes the rights of ethnic Russians in Ukraine are being violated. 
 
 In an article on the website of Britain's Guardian newspaper, Lavrov denied Russia was destabilizing Ukraine and accused the West of the "groundless whipping-up of tension". 
 
 Separately, he warned authorities in Kiev against any use of force against pro-Russian demonstrators. 
 
 The Russian Foreign Ministry later called on Ukraine to stop massing military forces it said were tasked with suppressing anti-government protests. 
 
 "We call for an immediate halt to military preparations which could lead to an outbreak of civil war," the ministry said in a statement. 
 
 Police said they cleared the protesters from the building in Kharkiv, but in Luhansk the demonstrators had seized weapons. 
 
 In Donetsk, home base of deposed Moscow-backed President Viktor Yanukovich, about 120 pro-Russia activists calling themselves the "Republican People's Soviet of Donetsk" seized the chamber of the regional assembly. 
 
 An unidentified bearded man read out "the act of the proclamation of an independent state, Donetsk People's Republic" in front of a white, blue and red Russian flag. 
 
 "In the event of aggressive action from the illegitimate Kiev authorities, we will appeal to the Russian Federation to bring in a peacekeeping contingent," ran the proclamation. 
 
 The activists later read out the text by loud hailer to a cheering crowd of about 1,000 outside the building. 
 
 RUSSIAN SPEAKERS 
 
 Putin announced on March 1, a week after Yanukovich was overthrown, that Moscow had the right to take military action in Ukraine to protect Russian speakers, creating the biggest confrontation between Moscow and the West since the Cold War. 
 
 The United States and EU imposed mild financial sanctions on some Russian officials over the seizure of Crimea and have threatened much tougher measures if Russian troops, now massed on the frontier, enter other parts of Ukraine. 
 
 Western European governments have hesitated to alienate Russia further, fearing for supplies of Russian natural gas, much of which reaches EU buyers via pipelines across Ukraine. Ukraine's own dependence on Russian gas gives Moscow strong leverage, especially over Ukraine's eastern industrial areas. 
 
 Russia's gas monopoly Gazprom said it had received no payments from Ukraine for money owed for gas and Kiev's arrears have now reached $2.2 billion. In previous years, gas disputes between Moscow and Kiev have hurt supplies to Europe. 
 
 NATO has halted cooperation with Russia. The Western military alliance announced on Monday it would now restrict access to its headquarters by Russian diplomats apart from Moscow's ambassador, his deputy and two support staff. 
 
 Mainly Russian-speaking eastern Ukraine, densely populated and producing much of the country's industrial output, has seen a sharp rise in tension since Yanukovich fled the country, and Kiev has long said it believes Moscow is behind the unrest. 
 
 Pro-Russian protesters briefly held public buildings in the east early last month and three people were killed in clashes in mid-March. But trouble had subsided until Sunday. 
 
 Unlike in Crimea, where ethnic Russians form a majority, most people in the east and south are ethnically Ukrainian, although they speak Russian as a first language. Eastern oligarchs who once backed Yanukovich have thrown their weight behind the government in Kiev, and the unrest there is a test of their ability to assert control. 
 
 (Additional reporting by Elizabeth Piper, Natalia Zinets and Pavel Polityuk, Writing by Richard Balmforth, Peter Graff and Timothy Heritage, editing by Elizabeth Piper and Andrew Heavens)
– Crimea first, eastern Ukraine next? Pro-Russia protesters last night seized government buildings in the cities of Kharkiv, Luhansk, and Donetsk in Ukraine's largely Russian-speaking east, waving Russian flags and demanding a referendum on joining Russia, reports Reuters. In Donetsk, separatists have dubbed the region an independent republic, and have called for the sovereignty referendum to be held by May 11, the AP reports, noting that Crimea did much the same before Russia annexed it. These self-proclaimed lawmakers have also asked Vladimir Putin to send peacekeeping troops, according to Russia's state-run ITAR-Tass news agency. Acting Ukrainian President Oleksandr Turchynov has canceled a trip abroad to deal with the unrest, and the country's interior minister, who blames the protests on Vladimir Putin and ousted Ukrainian leader Viktor Yanukovich, says the turmoil will be dealt with non-violently. He added that "separatists" had been removed from one building in Kharkiv as of today. More: Prime Minister Arseniy Yatsenyuk today emphasized those Russian fears, saying that country's troops were roughly 20 miles from the border and asserting that "an anti-Ukrainian plan is being put into operation ... under which foreign troops will cross the border and seize the territory of the country." Reuters reports that in Luhansk, protesters occupying the state security building have reportedly taken hold of weapons. Meanwhile, the New York Times reports that a Ukrainian military officer in Crimea was last night killed by a Russian soldier who fired an automatic weapon at the unarmed man. The death apparently resulted from a confrontation between a number of Ukrainian and Russian troops, and occurred in a military dorm. Some Ukrainian military personnel remain in Crimea to facilitate the transition, notes the Times.