US, Russian forces hunt 'white widow' kill squad feared inside Winter Olympics zone Ruzanna Ibragimova, the "white widow" of a dead terrorist, has reportedly travelled to Sochi where US counterterrorism agents are helping to locate her. Vengeful widow spotted outside foreign ministry near Sochi US and Russian security forces both hunting terror threat As many as four 'white widows' feared to be on the loose UP to four vengeful widows bent on murder have gone to ground inside the Winter Olympics zone, security agents fear, with only weeks until the Games open. American counterterrorism operatives have joined Russian security agents in the hunt for one particular 'jihadist white widow' who is thought to already be inside the security zone set up in Sochi. Ruzanna Ibragimova, the 22-year-old widow of a terrorist killed during the Moscow theatre attack, is believed to have travelled from Dagestan to Sochi on or around January 11. A known member of a Chechen jihadist group, she was recently spotted on the street outside the foreign ministry near Sochi, according to FoxNews.com sources. A bulletin put out by the Russian security force FSB states: "According to our information Ms Ibragimova may be used by the ringleaders of illegal armed groups for the organisation of terrorist acts in the zone of the 2014 Olympics." As the Sochi Winter Olympics draws near, the torch is carried in Volgograd, where two suicide bombings killed dozens last month. According to US security forces, "the notice is the first sign that terrorists may have managed to penetrate the security cordon." Ibragimova has been dubbed a "white widow" - the term used to describe jihadists' widows who seek to "blend in" to mount attacks. British woman Samantha Lewthwaite, the widow of 7/7 London suicide bomber Germaine Lindsay, became infamously referred to as a "white widow" after being implicated in several recent terror attacks. She is alleged to be a member of the Somali radical Islamic militant group al Shabaab and is now one of the world's most wanted terrorism suspects. But the term "black widow" is also prevalent as a description particularly of Chechen widows whose husbands have been killed in the ongoing fight against Russia. According to FoxNews.com there are fears as many as four "widows" could be on the loose in Sochi. US forces are working with their Russian counterparts inside the massive, 2,400km security zone set up to prevent attacks during the Winter Olympics. White widow ... Alleged terrorist Samantha Lewthwaite. "Russia has deployed 40,000 police and security personnel in a 'ring of steel' around Sochi to deter attacks by Islamist militants from the nearby North Caucasus republics," according to a US security bulletin. US and international experts have become increasingly concerned about security in the zone, in light of recent attacks and a call from Doku Umarov, the jihadist leader who has been described as Russia's Osama Bin Laden, for attacks and to stop Russia from hosting the Games. The news comes after a video was posted online by a group identifying itself as Vilayat Dagestan by two men claiming responsibility for recent suicide bombings of a train station and bus that killed 34 people in Volgograd. In the video, the men warn that other suicide attacks will follow. On hours before the video was released, President Vladimir Putin had assured visitors to Sochi that they would be safe. Security assurance ... Vladimir Putin has said visitors to Sochi will be safe. Security zone ... Russian officers check documentation on the streets of Sochi.