Moscow - Investigators have linked last week's suicide bombing at Moscow's busiest airport to a militant Islamist group from the Russian republic of Dagestan, authorities said on Monday.
There was clear evidence linking the attack at Domodedovo airport, in which 35 people were killed, to the terrorist leader Ibrahim- Khalil Daudov, authorities told the news agency Interfax.
It was the first time investigators have given details about the suspects behind the attack.
Daudov's wife had been killed while preparing explosives for the attack, they said. Her body was found after an explosion in a building near Moscow on December 31.
Violent attacks have been increasing recently in Dagestan, located in the North Caucasus, a region which includes the republics of Chechnya, Ingushetia, North Ossetia and Kabardino-Balkaria.
An attack on a freight train caused severe damage overnight on Monday.
Over the past three days police in Moscow have arrested seven people who had threatened further attacks in anonymous phone calls.
The threats had caused police to evacuate department stores and shopping centres. The would-be terrorists face up to three years in jail.
Investigators on Saturday said the suicide bomber himself had been a 20-year-old man from the North Caucasus but did not give a name.