In a video posted late Monday on a website affiliated with Islamic rebels in the Caucasus, Umarov said he ordered the Jan. 24 suicide bombing of Moscow's Domodedovo Airport and that more such attacks will follow, if Russia does not allow the region to become an independent state governed by sharia law.
The bombing of Domodedovo, Russia's largest airport, killed 36 people and injured about 180. Russian investigators said the bomber was a 20-year-old man from the Caucasus region that includes Chechnya, but have not released his name or other details.
Parliament was briefed Tuesday in a closed session, and no details were immediately released.
"You see this special operation carried out by my order ...
more special operations will be carried out in the future," Umarov said in the video, wearing a camouflage uniform and a skullcap.
"Among us there are hundreds of brothers who are prepared to sacrifice themselves" in further attacks, he said. "We can at any time carry out operations where we want."
Umarov said that the rebels will continue their fight to free the Caucasus from Russian rule and voiced solidarity with Islamic militants in Afghanistan, Iraq and Pakistan.
The Federal Security Service, the KGB successor agency charged with fighting terrorism, refused on Tuesday to comment on Umarov's claim.
Over the weekend, the website released another video in which Umarov also threatened more attacks, saying 2011 would be "the year of blood and tears" and that he could call on 50 to 60 suicide bombers if necessary.
Chechen rebels have fought two full-scale wars against Russian forces since 1994. Major offensives in the second war died down about a decade ago, but the Islamic insurgency has spread increasingly across neighboring North Caucasus provinces.
Umarov, who became the top Chechen military leader in 2006, has claimed responsibility for an array of terrorist attacks, including last year's double suicide bombing of the Moscow subway system that killed 40 people. However, some observers see him more as an ideological than a military figure as many terrorist cells operate autonomously and shun centralized command.
The blast at Domodedovo raised new doubts about Russia's strategy against the insurgents and about its ability to protect against future attacks.
President Dmitry Medvedev has fired several top transport police officials and ordered heightened security measures at all the country's main transport hubs, including major railway stations.
The attack took place as Medvedev was preparing to speak at the prestigious World Economic Forum in Davos, Switzerland, where he hoped to reassure foreign investors that Russia was safe and attractive.