Instructions: In this task, you are given a text of many news articles seperated by special token "|||||". Your task is to summarize them.
Input: Counter-terrorism police have opened an investigation into the “unexplained” death on British soil of an arch enemy of Vladimir Putin, just eight days after the nerve gas assassination attempt on a Russian double agent. 
  
 Nikolai Glushkov, 68, the right-hand man of the deceased oligarch Boris Berezovsky, Mr Putin’s one-time fiercest rival, was found dead at his London home on Monday. 
  
 A Russian media source said Glushkov, the former boss of the state airline Aeroflot, who said he feared he was on a Kremlin hit-list, was found with “strangulation marks” on his neck. 
  
 The inquiry into Glushkov’s death was announced hours before a midnight deadline for the Kremlin to explain how Russian-made nerve... ||||| A Russian exile who was close friends with the late oligarch Boris Berezovsky has been found dead in his London home, according to friends. 
  
 Nikolai Glushkov, 68, was discovered by his family and friends late on Monday night. The cause of death is not yet clear. One of his friends, the newspaper editor Damian Kudryavtsev, posted the news on his Facebook page. 
  
 Without confirming the man’s name, the Metropolitan police said the counter-terrorism command unit was leading the investigation into the death “as a precaution because of associations that the man is believed to have had”. 
  
  
  
 It said there was no evidence at present to suggest a link to poisoning in Salisbury of the Russian former double agent Sergei Skripal and his daughter, Yulia. The Skripals remain in a critical condition. 
  
  
  
 Police were called by the London ambulance service to a residential address in New Malden at 10.46pm on Monday. “An investigation is under way following the death of a man in his 60s in Kingston borough,” said the Met. 
  
 On Tuesday a cluster of blue tents had been erected to cover the front of Glushkov’s house and several uniformed police stood in front of a cordon. 
  
 Facebook Twitter Pinterest A policeman stands guard outside the house of Nikolai Glushkov. Photograph: Will Edwards/AFP/Getty Images 
  
 Glushkov’s neighbours painted a picture of a man living a quiet life in south-west London, where he had recently been recovering from an operation. 
  
  
  
 Ako Mohammed, who runs a barber shop near Glushkov’s home, said the Russian had last come in more than a fortnight ago. 
  
 “He was using crutches and had just had an operation on his leg,” he said. “He used to come in every month or so. He was in last about two or three weeks ago and asked us how business was.” 
  
 Kate Fitzsimmons, 87, who has lived on the street for more than 30 years, said Glushkov would occasionally wave and smile to her when he came out of his house, directly across from hers. “He seemed like a quiet man. A lady would come sometimes as well but he kept to himself generally.” 
  
  
  
 In the 1990s Glushkov was a director of the state airline Aeroflot and Berezovsky’s LogoVAZ car company. In 1999, as Berezovsky fell out with Vladimir Putin and fled to the UK, Glushkov was charged with money laundering and fraud. He spent five years in jail and was freed in 2004. Fearing further arrest, he fled to the UK and was granted political asylum. 
  
 In 2011 he gave evidence in a court case brought by Berezovsky against fellow oligarch Roman Abramovich, who remained on good terms with the Kremlin. Glushkov told the court he had effectively been taken hostage by Putin’s administration, which wanted to pressure Berezovsky to sell his stake in the TV station ORT. 
  
 In court, Berezovsky claimed he and Abramovich had been partners in the 1990s in an oil firm, Sibneft, and accused the Chelsea football club owner of cheating him out of $5bn (£3.2bn). Abramovich denied this. The judge, Mrs Justice Gloster, rejected the claim and described Berezovsky as “deliberately dishonest”. 
  
 Glushkov was unhappy with the judgment and launched a formal appeal, citing “bias”. Meanwhile, Berezovsky disappeared from public life. In March 2013 he was found dead at his ex-wife’s home in Berkshire. Police said they believed he killed himself but his friends were not so certain, and a coroner recorded an open verdict. 
  
 Speaking to the Guardian in 2013, Glushkov said he was sceptical that Berezovsky, who was found hanged in a bathroom, took his own life. “I’m definite Boris was killed. I have quite different information from what is being published in the media,” he said. 
  
 He noted that a large number of Russian exiles, including Berezovsky and Alexander Litvinenko, had died under mysterious circumstances. “Boris was strangled. Either he did it himself or with the help of someone. [But] I don’t believe it was suicide,” Glushkov said. “Too many deaths [of Russian emigres] have been happening.” 
  
 Glushkov continued to investigate the circumstances surrounding Berezovsky’s death for some months. He conceded that in the period before his friend’s death they had quarrelled. In 2013 Glushkov emailed a friend: “I have a lot of new facts that are of great interest.” 
  
 Glushkov has two adult children, Natasha and Dima, and an ex-wife who lives in Moscow. It is understood he had split in recent years from a partner, although they remained on good terms. Natasha is based in the UK. 
  
 In 2017, during a trial in absentia in Russia, Glushkov was sentenced to eight years in prison for stealing $123m from Aeroflot. The airline pursued the case in London. Glushkov had been defending himself, and told friends he had run out of money to hire lawyers. He was due to attend a hearing at 10.30am on Monday in the Rolls building, London’s commercial court, but failed to show up. 
  
 The Met said the next of kin had been informed. “Whilst we believe we know the identity of the deceased, formal identification is yet to take place,” the force said. “The death is currently being treated as an unexplained.” ||||| LONDON (Reuters) - U.S. President Donald Trump and British Prime Minister Theresa May agreed on Tuesday that Russia must provide “unambiguous answers” after London gave Moscow until midnight to explain how a Soviet-era nerve weapon was used against a former Russian double agent. 
  
 May, who said on Monday it was “highly likely” that Russia was behind the poisoning of Sergei Skripal and his daughter, also won support from Britain’s main European allies and the European Union, which denounced the attack as “shocking” and offered help to track down those responsible. 
  
 Jens Stoltenberg, Secretary-General of the U.S.-led NATO alliance, said the attack was “horrendous”. 
  
 Russia, however, signalled there was little likelihood that it would respond adequately to London’s call for a credible explanation by Wednesday. 
  
 Denying it had played any part in the attack, which left the 66-year-old Skripal and his 33-year-old daughter Yulia fighting for their lives, Russia said it would ignore the ultimatum until London handed over samples of the nerve agent used and complied with international obligations for joint investigations of such incidents. 
  
 “Any threats to take ‘sanctions’ against Russia will not be left without a response,” the Russian foreign ministry said in a statement. “The British side should understand that.” 
  
 Russia holds a presidential election on Sunday in which Vladimir Putin, himself a former KGB spy, is expected to coast to a fourth term in the Kremlin. 
  
 Skripal, a former officer with Russian military intelligence, betrayed dozens of Russian agents to British intelligence before being arrested in Moscow and jailed in 2006. 
  
 He was released under a spy swap deal in 2010 and took refuge in Britain, where he had been living quietly in the cathedral city of Salisbury until he and his daughter were found unconscious on a public bench there on March 4. 
  
 A British policeman who was also affected by the nerve agent is now conscious in a serious but stable condition. 
  
 LETHAL NERVE AGENT 
  
 May said on Monday Britain had identified the substance as belonging to the lethal Novichok group of nerve agents developed by the Soviet military in the 1970s and 1980s. 
  
 She and her ministers say Britain will take further “robust” punitive action against Russian interests - beyond sanctions already in place - if Putin does not come up with a credible explanation of events. 
  
 Trump’s endorsement of Britain’s tough line, made during a phone call with May, came on the heels of messages of solidarity from France’s President Emmanuel Macron and German Chancellor Angela Merkel. They gave the British prime minister additional hope of marshalling Western backing for her government as it heads towards a showdown with Putin. 
  
 Members of the emergency services wearing protective clothing work near the bench where former Russian intelligence officer Sergei Skripal and his daughter Yulia were found poisoned in Salisbury, Britain, March 13, 2018. REUTERS/Henry Nicholls 
  
 “President Trump agreed with Prime Minister May that the Government of the Russian Federation must provide unambiguous answers regarding how this chemical weapon, developed in Russia, came to be used in the United Kingdom,” the White House said in a statement about the two leaders’ phone call. 
  
 “The two leaders agreed on the need for consequences for those who use these heinous weapons in flagrant violation of international norms,” it said. 
  
 May’s spokesman said Trump had said the United States was “with the U.K. all the way”. 
  
 If no satisfactory Russian response is received by midnight London time May is likely to outline Britain’s response in parliament on Wednesday. 
  
 It remains to be seen how much of a rupture in relations with Russia May’s government is prepared to envisage. 
  
 While trade figures show Russia accounts for less than 1 percent of British imports, London is of major importance for Russian companies seeking to raise capital and since the 1991 collapse of the Soviet Union has become the Western capital of choice for many Russian business leaders. 
  
 Britain could call on allies for a coordinated Western response, freeze the assets of Russian business leaders and officials, expel diplomats or launch targeted cyber attacks. It may also cut back participation in the soccer World Cup which Russia is hosting in June and July. 
  
 Russia Today, a round-the-clock news network that is funded by Putin’s government, could lose its licence to broadcast in Britain if May’s government determined that Moscow was behind the attack, Britain’s media regulator said. 
  
 Slideshow (11 Images) 
  
 This report drew a swift response from Russia. “Not a single British media outlet will work in our country if they shut down Russia Today (RT),” the state-run RIA news agency cited Maria Zakharova as saying on state television. 
  
 The expression of solidarity from the EU came despite tensions over British preparations to quit the bloc next year. 
  
 The EU has already imposed travel restrictions and asset freezes against 150 people and 38 companies in response to Russia’s annexation of Crimea from Ukraine. EU nationals and companies are also banned from buying or selling new bonds or equity in some state-owned Russian banks and major Russian energy companies. 
  
 But diplomats in Brussels said that, despite sharing Britain’s anger, the bloc was unlikely to have much stomach for imposing additional sanctions on Russia since attributing the nerve attack to Moscow was difficult and keeping existing economic sanctions going was proving a strain. |||||
Output:
The two Russians had fled to the UK, and now both are dead. Nikolai Glushkov, who was once business partners with Boris Berezovsky, was found dead in his London home Monday night. Counterterrorism police are investigating the unexplained death "as a precaution because of associations that the man is believed to have had." The Telegraph calls Berezovsky, who opposed Putin and also died in unexplained circumstances in the UK in 2013, Putin's "arch enemy"; Glushkov and other friends insisted Putin ordered his murder. The paper calls Glushkov Berezovsky's "closest aide"; in the '90s he was a director at Berezovsky's car company as well as the state airline Aeroflot. Glushkov, variously reported as 68 or 69, left Russia for the UK, where he was ultimately granted political asylum, after Berezovsky fell out with Putin and left for the UK himself. After Berezovsky's exit, Glushkov was charged with money laundering and fraud and spent five years in jail. He left for the UK out of fear he'd be arrested again; he denied all the charges against him. The Guardian has much more on that period of his life. Glushkov's death comes eight days after the poisoning of Russian double agent Sergei Skripal, but authorities say there is no evidence the two incidents are connected. In the Skripal case, Reuters reports Britain gave Russia a deadline of midnight Tuesday to explain how a Russian nerve agent was used against him, but Russia has pledged not to do so until samples of the nerve agent are handed over. President Trump Tuesday expressed support for Britain, saying if the US "agrees" with the facts, "we will condemn Russia or whoever it may be."