President Dmitry Medvedev vowed to track down and punish those behind the bombing, which also injured over 150 people, during the busy late afternoon at Moscow's Domodedovo airport. The dead included some foreigners.

Islamist rebels have vowed to take their bombing campaign from the North Caucasus to the Russian heartland in the year before presidential elections, hitting transport and economic targets. They have also leveled threats at the 2014 Winter Olympics, scheduled for the Black Sea resort town of Sochi, a region some militants consider "occupied."

Dense smoke filled Domodedovo's international arrivals hall and a fire burned along one wall. Thick drops of blood were scattered across the snow-covered tarmac outside the arrivals hall, where Interfax news agency said traces of shrapnel were found.

Two Britons were among the dead, media cited investigative committee spokesman Vladimir Markin as saying, and French, Italians, and Germans were in hospitals.

The prosecutor's office said the bomb had been classified as a terrorist attack - the largest since twin suicide bombings on the Moscow metro rocked the Russian heartland in March.

US President Barack Obama condemned the "outrageous act of terrorism" and offered Moscow help. NATO Secretary General Anders Fogh Rasmussen said he was shocked, state TV said.