A leading Chechen militant claimed responsibility for the Jan. 24 suicide bombing of Moscow' Domodedovo airport that killed 36 people and injured scores more.
Doku Umarov appears in a 16-minute video released on the internet, claiming the "martyr operation" was carried out on his orders.
In the video, Umarov says the Muslims of the Caucasus were 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.
While the Chechen's claim of responsibility has not been verified, 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 Moscow Metro attack that killed 40 in March 2010. U.S. and Russian officials believe he was behind that bombing.
Umarov, shown sitting cross-legged in the video wearing camouflage, described the attack on Domodedovo airport as a special operation directed against the Russian people as well as Russian Prime Minister Vladimir Putin, Reuters reported.
Umarov's statement came just two days after he released a video in which he is flanked by two men -- one of which he reportedly claimed was heading to Moscow to carry out a special mission. In that video, he promises more attacks on Russia.
Blast Ownership Unconfirmed, But Fits a Pattern, Expert Says
The blast erupted in the arrivals area of the Domodedovo airport at 4:40 p.m. Moscow time Jan. 24. In addition to the 36 dead, another 130 were injured in what investigators called a suicide bombing at the country's busiest airport.
Initial reports published by Russia's state news agency RIA said witnesses had seen two suicide bombers carry out the attack. Later reports pointed to a single attacker. On Twitter, one purported eyewitness, Ilya Likhtenfeld, said the bomb was on a man standing in a crowd near a cafe.
Video taken inside the airport apparently minutes after the bombing shows the blast area full of smoke, with luggage scattered around the ground. Several bodies, prone and unmoving on the ground, are also visible.
No hard evidence has emerged yet to link the Domodedovo bombing to any specific terrorist group, but, according to former White House counter-terror adviser and ABC News consultant Richard Clarke, it fits the pattern of a persistent Chechen campaign of violence.
"This is part of a pattern where the Chechen rebel group attacks in Moscow or in Russia -- a major attack about every two years," Clarke told ABC News following the bombing. "They've attacked in the Metro, they've attacked in schools, they've attacked in apartment buildings… This is a regular pattern."
Suicide bombers, often female, from Chechnya or Dagestan and sometimes known as "black widows," have carried out many attacks on Russian targets in the past decade, including the simultaneous bombings of two planes mid-flight that killed 90 people in the summer of 2004 and a Moscow Metro bombing that killed 10 a week later.
Chechen Militant Leader Had Warned of Attacks to Come
"Black widows" are often avenging the deaths of relatives at the hand of federal forces.
Last March, two female suicide bombers attacked the Moscow subway, killing 40 people and injuring more than 100.
Both women were from Dagestan in the restive North Caucasus region where Russian forces have been battling an Islamist insurgency. One was a 28-year-old schoolteacher, the other the 17-year-old widow of a local militant leader who was killed by Russian forces in 2009.
On Jan. 21, three days before the Domodedovo bombing, Russia's prime minister, Vladimir Putin said Russia must combat terrorism in the North Caucasus by improving the quality of life for the people there.
"Our objective is to radically change the situation in the North Caucasus, primarily by improving the quality of life of the people, ensuring their security and giving them the opportunity to work and live in peace," Putin said. "We must eradicate the roots of terrorism and extremism, first of all poverty, unemployment, ignorance and inadequate levels of education, and corruption and lawlessness."
The Associated Press contributed to this report.