Image copyright AFP Image caption With Geneva on high alert, the city's airport was evacuated after a suspect package was found 
 
 Two people of Syrian origin have been arrested in Geneva on suspicion of making, concealing and transporting explosives, the Swiss attorney general says. 
 
 The two are also suspected of violating a law prohibiting groups such as al-Qaeda and the so-called Islamic State (IS), the statement added. 
 
 Geneva's prosecutor said traces of explosive had been found in their car. 
 
 Geneva has been on high alert this week amid fears an IS cell was in the area. 
 
 Swiss President Simonetta Sommaruga said on Friday that a "foreign authority" had provided the information about "a potential IS cell in the Geneva area" but there was no indication that "a concrete attack" was planned. 
 
 Image copyright AP Image caption Checks have been increased on the French-Swiss border near Geneva 
 
 Image copyright AP Image caption Security was tightened outside France's consulate in Geneva 
 
 Geneva's Prosecutor Olivier Jornot told a news conference that the two Syrians had just arrived in the Swiss city and could not speak French when they were arrested on Friday. 
 
 They "were stopped by Geneva police... because of the increased vigilance required from the police force," he said. "These people, because of their behaviour and nationality, were subject to more careful checks, and these checks revealed traces of explosives in the car they were using." 
 
 He confirmed no evidence of toxic gas was found. 
 
 An earlier statement from the prosecutor's office said criminal proceedings had been opened against them under Switzerland's law against the manufacture and transport of explosives and toxic gases. 
 
 The tip-off about a terror cell in Geneva had originally come from the United States, Swiss media reported on Friday. 
 
 Daily newspaper Le Temps, quoting a source close to the investigation, said US intelligence had identified three jihadist cells in Chicago, Toronto and Geneva. 
 
 On Thursday, security was stepped up outside synagogues, the UN building and the French ambassador's home, as well as train stations, the airport and similar places. 
 
 The number of police on Geneva's streets has been increased. 
 
 UN spokesman Michele Zaccheo said there was "no specific threat to the UN in Geneva or its personnel". 
 
 The border with France runs through the outskirts of Geneva. 
 
 IS said it carried out the attacks in Paris on 13 November which killed 130 people. 
 
 Two men linked to the attacks - Salah Abdeslam and Mohammed Abrini - are still on the run and investigations have been launched in several European countries. ||||| Geneva (AFP) - Swiss authorities on Saturday said two Syrians had been arrested in Geneva after traces of explosives were found in their car, as police continued to hunt for several suspected jihadists with links to the Islamic State group. 
 
 Geneva prosecutor Olivier Jornot told a news conference that the two men had Syrian passports and only "recently arrived" in Switzerland. They spoke Arabic, he added. 
 
 They were arrested after police were alerted about "their behaviour". 
 
 He sidestepped questions on whether the pair were on visas allowing them to circulate freely through the visa-free Schengen zone. 
 
 But Jornot said they were not among the four men being searched as suspected jihadists planning attacks following the Paris carnage on November 13 and whose photographs have been released by the police. 
 
 Jornot said the two arrested men said they had recently bought the car they were travelling in and clarified that it only bore traces of explosives and not toxic gases. 
 
 View gallery Geneva's attorney general Olivier Jornot speaks during a press conference on December 12, 2015 ( … 
 
 He said they were arrested on the day they arrived in Switzerland. 
 
 The federal prosecutor's office had said in a statement earlier Saturday that the two men were arrested on suspicion of the "manufacture, concealment and transport of explosives and toxic gases" and of violating Swiss law prohibiting "groups like Al-Qaeda, Islamic State and similar organisations". 
 
 Jornot later clarified that "the vehicle was at one point used to transport explosives" but that it did not necessarily mean it was the two suspects who did so. 
 
 The arrests come with the city on edge after Swiss authorities on Thursday opened a probe relating to a "terrorist threat in the Geneva region", prompting the region to raise its alert level to three on a five-point scale. 
 
 Armed police were deployed at sensitive locations across Geneva, which borders France and is home to the United Nations' European headquarters. 
 
 The Le Temps daily on Friday cited an unnamed source close to the case as saying the Swiss had received a tip-off from US intelligence about a jihadist cell in Geneva. 
 
 Pictures of four individuals suspected of links to the Islamic State group, which claimed last month's Paris attacks, were published by media across the country. 
 
 Authorities in Geneva had said that the search for possible extremists was being conducted "in the context of the investigation following the Paris attacks". 
 
 But multiple sources, who requested anonymity, said there did not appear to be a direct link with the coordinated November 13 gun and suicide bombing attacks that left 130 dead in the French capital. ||||| (CNN) European counterterrorism agencies scrambled Friday to assess the potential danger of a complex and growing terrorism threat exposed by the arrests of more than two dozen people with suspected links to Islamic extremists. 
 
 As many as 20 sleeper cells of between 120 and 180 people could be ready to strike in France, Germany, Belgium and the Netherlands, a Western intelligence source told CNN. 
 
 European Union and Middle East intelligence agencies had identified an "imminent threat" to Belgium, and possibly to the Netherlands, the source told CNN. 
 
 "There is a tremendous amount of concern over sleeper cells in Europe," said Western official with direct knowledge of the situation. 
 
 Authorities worry about a rash of copycat attacks throughout Europe, according to the official, who compared the problem to "a slow-motion car accident happening right in front of us." 
 
 Intelligence officials in Europe were trying to determine the nature of the wider threat, a senior European counterterrorism official told CNN. They were monitoring groups of men who have returned from fighting in Syria. 
 
 It is believed ISIS directed the men to return to Europe to launch attacks in retaliation for airstrikes against the terror group in Syria and Iraq, according to the official. 
 
 Overall, authorities made 17 arrests related to the Belgium threat -- 13 in Belgium and four at two locations in France. 
 
 Here are the latest developments related to the terror threat in the West: 
 
 • The suspected Islamist terrorists who had a shootout with police on Thursday in Verviers, Belgium, have ties to ISIS-linked cells in other European countries, a senior Belgian counterterrorism source told CNN's Paul Cruickshank. The two suspects who died in the shootout are believed to have fought with ISIS in Syria, the source said. 
 
 • A total of 122,000 police officers, gendarmes and military personnel are deployed across France as part of the security plan, Interior Minister Bernard Cazeneuve said. 
 
 • There does not appear to be a command-and-control element to last week's Paris attacks at the offices of Charlie Hebdo magazine and two additional locations other than a general "go forward and do something," the Western official with direct knowledge told CNN. The attacks were "highly franchised terrorism with general instructions." 
 
 • Sectarian turmoil in Yemen is bolstering al Qaeda in the Arabian Peninsula's (AQAP) local recruitment and buying it space for attacks against the West and train the next generation of bomb makers, according to one Western diplomat. 
 
 • Metropolitan Police Assistant Commissioner Mark Rowley, Britain's senior counterterrorism officer, said additional police patrols were being put in place at Jewish community centers, synagogues and schools. 
 
 • An 18-year-old woman was arrested at Stansted Airport near London on suspicion of terrorism offenses, London's Metropolitan Police said on Twitter. 
 
 • British Prime Minister David Cameron called on his country and the United States to fight the "poisonous ideology" behind the terrorist attacks that killed at least 17 people in France this month. "Britain and America both face threats to our national security from people who hate what our countries stand for and are determined to do us harm," Cameron said at a White House news conference with President Barack Obama. 
 
 • Obama promised to "do everything in our power" to assist France in its effort to combat terrorism. 
 
 • Two people suspected of involvement with the alleged terror cell in Verviers were detained trying to cross from France into Italy through the Frejus tunnel, a spokesman for Belgium's federal prosecutor's office said. 
 
 • Belgian federal prosecutor Eric Van der Sypt said 13 people were arrested in a dozen anti-terror raids . Authorities believed the "threat of a terrorist attack was very imminent." 
 
 • The suspected terror cell, which included people returning from Syria, planned to target police officers, Van der Sypt said. Police said they recovered weapons, bomb-making materials and police uniforms. 
 
 • Belgium put 150 troops on standby for anti-terror operations. 
 
 • At least a dozen people were detained in the Paris region overnight in connection with last week's shootings in Paris, the city prosecutor's office said. 
 
 • Two men in their early 40s were arrested in Berlin on suspicion of links to ISIS , police said. They did not appear to have been planning attacks. Berlin police spokesman Stefan Redlich said the investigation had started a year ago; the police operation planned several weeks ago. 
 
 • The Netherlands said it was not raising its terror threat level, currently at "substantial," the second-highest . "That means there is a realistic threat, but no concrete or specific information of an attack," said government spokesman Edmond Messchaert. 
 
 • The current level of security in Belgium will remain for at least one month and will then be evaluated to determine if it needs to be modified, the country's prime minister said late Friday. "From the time we are confronted with an increase in the threat, we went to level 3 on a scale of 4; we must mobilize the resources available," Charles Michel told CNN affiliate RTL. 
 
 Following up on Paris attacks 
 
 European counterterrorism agencies have been trying to identify and thwart potential threats after the deadly attacks in Paris last week, in which 17 people were killed. 
 
 Security services are working to track those associated with the attackers: brothers Said and Cherif Kouachi and Amedy Coulibaly. 
 
 Neetin Karasular, a suspected Belgian trafficker in weapons who met with Coulibaly's widow, Hayat Boumeddiene, is in custody, Karasular's attorney, Michel Bouchat, told CNN. 
 
 Karasular was charged with association with wrongdoers and firearm offenses, in Charleroi, Belgium. But his attorney said the arrest was not connected to the other Belgian raids. 
 
 Graphic shows the links between the Paris suspects and a wider network. 
 
 Coulibaly, who attacked a kosher supermarket in Paris last Friday, pledged allegiance to ISIS. 
 
 However, the Kouachis , the men who French authorities say carried out the deadly shooting at the offices of the French satirical magazine, are believed to have had links to AQAP , which has claimed responsibility for the shootings. 
 
 A European counterterrorism official told CNN that there were indications that ISIS leadership had directed returnees from Iraq and Syria to launch attacks in Europe in revenge for Syria and Iraq airstrikes. 
 
 The official, who cited France, the United Kingdom and Belgium as countries facing a particular threat, said counterterrorism agencies in Germany are on high alert. 
 
 Several European nations, including the United Kingdom, France, Belgium and the Netherlands, are participating in the air campaign against ISIS in Iraq.
– Two people from Syria were arrested on terror charges Friday in Geneva and traces of explosives were found in their vehicle, AFP reports. The arrests come after Swiss authorities received a tip from US intelligence that indicated an ISIS cell was active in Geneva, according to the BBC. ABC News reports Geneva raised its terror threat level Thursday in response to the tip. According to AFP, the arrested men have been accused of the "manufacture, concealment, and transport of explosives and toxic gases" and of supporting "groups like Al-Qaeda, Islamic State, and similar organizations." The arrests were announced as part of a "terror probe" by Swiss authorities Saturday, AFP reports. Police have been deployed around Geneva as the city remains on alert. In addition to being the UN's European headquarters, many international organizations active in Syria—including the International Organization for Migration and UN High Commissioner for Refugees—are also based in Geneva, according to ABC. The BBC reports the same source who claims US intelligence found an active ISIS cell in Geneva also states two more were identified in Chicago and Toronto.