(USA TODAY) -- U.S. authorities were working to determine the credibility of a possible new threat to the Sochi Olympics that surfaced Sunday.
News reports indicated that Islamist militants in Russia released a video recorded by two suicide bombers who said the Olympics will not be safe because of the presence of Russian forces in the North Caucasus region. The opening ceremony will be held in 18 days in the Black Sea resort city of Sochi.
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The video included security footage of two suicide bombings in Volgograd.
Authorities in the U.S. were analyzing the video posted on the extremist website, and it was immediately unclear whether the boasts of the two unidentified men represented a credible threat to the Games, a federal law enforcement official said Sunday.
The official, who is familiar with the video but not authorized to comment publicly, said there was no definitive evidence to indicate whether the two men pictured in the video were linked to last month's bombings in the city of Volgograd, which left more than 30 people dead. Volgograd is nearly 400 miles from the Olympic host city of Sochi.
The attacks on the city, a major transportation hub, underscored the threat posed by extremists in the volatile Caucasus region.
"We'll have a surprise package for you," the men in the video said, according to the report. "And those tourists that will come to you, for them, too, we have a surprise. ... This will be our revenge."
Russian president Vladimir Putin and government officials have reassured visitors for months that the country's security forces will do everything they can to keep the Games safe. On Sunday, he reiterated the point, according to CNN.
"We will draw on the experience acquired during similar events held in other regions of the world and in other countries," said Putin, who added 40,000 law enforcement and special services officers will be deployed for security. "It means that we will protect our air and sea space, as well as the mountain cluster."
The Sochi Olympics will be held in two clusters - with ice sports such as hockey and figure skating on the coast and skiing and sliding sports in the mountains.
Putin said security will be visible but visitors should feel welcome.
"We will try to make certain that the security measures are not intrusive or too conspicuous, so they are not too noticeable for the athletes, the Olympics' guests or journalists," Putin said.
The Volgograd bombings in December have raised security concerns. On Sunday, Sen. Angus King of Maine said on CNN he wouldn't go to the Sochi Olympics and he wouldn't send his family.
"We don't seem to be getting all of the information we need to protect our athletes in the games," said Rep. Mike Rogers, chairman of the House Intelligence Committee. "I think this needs to change, and it should change soon."
While the teams are still being selected for some U.S. winter sports, several athletes have said they're aware of the concerns but they have confidence in Russia's security plan.
The State Department issued a travel alert Jan. 10 to U.S. citizens attending the Games, cautioning them to be "aware of their personal surroundings and follow good security practices." It said there is no indication of a specific threat to Americans.
Last week Chechen leader Ramzan Kadyrov said Doku Umarov, who made threats against the Games, has died. He had no proof of Umarov's death but said the information was obtained through communications between other rebel leaders.