Umarov sat wearing camouflage fatigues and a cap in front of a black jihadist flag, flanked by two fighters who, like him, were bearded. As he spoke, birds could be heard singing in the forest.

Sochi, which is due to host the Games next February, is a few hundred kilometers from the volatile and mountainous North Caucasus region, where there is almost daily violence.

Putin has promised tight security at the Games, on which Russia is spending more than $50 billion, and sees it as a chance to show the world what his nation can achieve.

"They [Russia] plan to hold the Olympics on the bones of our ancestors, on the bones of many, many dead Muslims, buried on the territory of our land on the Black Sea, and we as mujahideen are obliged not to permit that, using any methods allowed us by the almighty Allah," Umarov said in the four-minute video on a popular rebel website.

"I call on you, every mujahid, either in Tatarstan, Bashkortostan or on the territory of the Caucasus to use maximum force on the path of Allah to disrupt this Satanic dancing on the bones of our ancestors," he said.
The Kremlin declined comment on the video, the authenticity of which could not immediately be established. Umarov has, however, regularly used online videos to send messages to the Islamic fighters he refers to as mujahideen.

Russia's most wanted man, Umarov leads a group called the Caucasus Emirate, which has taken responsibility for organizing many attacks, including suicide bombings that killed 37 people at a Moscow airport in 2011 and at least 40 people on the Moscow subway in 2010.

Putin expressed concern last year that violence involving Muslims could spread to Tatarstan, in central Russia, after the top Muslim official there was wounded in a bomb attack.

In February 2012, Umarov ordered a moratorium on attacks on Russian targets outside the North Caucasus and called for a halt on attacks that would harm civilians, but made clear in the new video that this order had been rescinded.

The 2012 order was issued at the height of a protest movement against Putin's more than decade-long rule and before last year's presidential election, which Putin won.

But the protests have dwindled and Russia has killed a number of insurgency leaders, including Umarov's right-hand man in the Ingushetia region.

Putin has long taken a tough stance against violence in the North Caucasus after two wars between the Russian army and Chechen separatists.
Wary of violence spilling over at the Games, Russia has stepped up cooperation with the United States over security since the Boston bombings, in which two ethnic Chechens are the

main suspects. One spent time in the region before the bombings.

"Umarov is announcing this now to increase the Caucasus Emirate's visibility by using Sochi, which has attained international recognition before the Olympic Games," said Mairbek Vatchagayev, a former Chechen official and an expert on the region.

Analysts are divided over the Caucasus Emirate's ability to carry out a large-scale bomb attack on Sochi, but Umarov has been under pressure from some of his supporters to repeal the moratorium on attacks outside the North Caucasus.

"There is enough time to try to plan a terrorist attack and to carry it out," Vatchagayev said.