An explosion at Domodedovo Airport in Moscow has killed 31 people, according to reports.
Sergei Markin of the Russian Investigative Committee confirmed reports of the explosion at the busiest of the city's three commercial airports, but said he had no further details.
Russian news agencies said the blast was believed to have happened inside the airport's international arrivals hall.
One passenger, identified only as Viktor, told how he heard a bang outside the airport, where he was waiting for a car.
"There was an explosion, a bang. Then I saw a policeman covered in fragments of flesh and all bloody. He was shouting 'I've survived! I've survived!'"
Domodedovo is generally regarded as Moscow's most up-to-date airport, but its security procedures have been questioned.
In 2004, two suicide bombers were able to board planes at Domodedovo by buying tickets illegally from airport personnel. The bombers blew themselves up in mid-air, killing all 90 people aboard the two flights.
In more recent suicide bombings in Moscow, twin blasts in the Metro last March killed 39 people and wounded more than 60.
In December 2009, Chechen rebels blew up a high-speed train between Moscow and St Petersburg, killing 26 people and injuring scores.