Chechen who claimed Russian airport bombing threatens more attacks (VIDEO)

Doku Umarov, the Chechen rebel leader who claimed that he was behind the deadly Moscow airport bombing last month, has said that Russia faces a year of "blood and tears" if it refuses to abandon its North Caucasus territories.

Umarov, 46, appearing in a 16-minute video apparently made on the day of the Jan. 24 attack that killed 36 people at Moscow's Domodedovo airport and released on an Islamist website Monday, says: "The special operation today in Moscow … was carried out on my orders."

He said there would be further such attacks in pursuit of an independent Muslim state governed by Shariah law in Russia's Caucasus region — a territory embracing Chechnya, Dagestan and other nearby territories.

In the video, Umarov — wearing combat fatigues, talking quietly and hesitantly — says the Muslims of the Caucasus are at war with the Russian "occupation" and says the attacks will continue, according to Kavkaz Center, a Chechen news outlet that posted the statement from Umarov.

A senior U.S. official told ABC News Umarov's past claims of responsibility gave him credibility. "We would not be surprised to learn that he is in fact behind the [airport] attack," the official said.

Umarov also claimed the twin suicide bombing in Moscow's crowded metro system last March that killed 40 people. U.S. and Russian officials believe he was behind that bombing. Some reports link Umarov to the 2004 Beslan school siege in which 334 hostages – including 186 children – died.

In the video, the bearded Umarov said "a brother" was being sent to Moscow to carry out an unspecified special operation, apparently the young man standing at his left.

Russian officials last week said the Domodedovo suicide bomber was a 20-year-old native of the North Caucasus, though they did not release his name, citing the ongoing investigation.

"We have to carry out our operation in order to wake you up. If this is not enough, then God willing, other blows will follow," Umarov said.

"I can tell you with 100 percent confidence … if God is with us then this year will be a year of blood and tears," he said.

Umarov calls himself "Emir Dokku Abu Usman" and proclaims himself leader of an Islamic "caliphate" that seeks to wrest from Moscow's rule virtually the entire northern slope of the Caucasus Mountains, including seven autonomous Russian republics strung out between the Caspian and Black seas.