A suicide bomber killed more than 30 people and injured about 140 when he blew himself up in a packed terminal at Moscow's busiest airport today.
The city was immediately put on a terror attack alert with extra police patrolling transport and other likely targets.
"From the preliminary information we have, it was a terror attack," President Dmitry Medvedev said, saying it was clear that security had failed.
It was not the first time Domodedovo airport's security has been breached.
In 2004 two suicide bombers were able to board planes by buying tickets illegally from airport staff. The women blew themselves up in mid-air, killing all 90 people on the two flights.
The airport insists that security is one of its top priorities, claiming that its "cutting-edge operations technology guarantees the safety of passengers' and guests' lives."
Today's blast left the arrivals terminal at Domodedovo engulfed in smoke and splattered with body parts.
Amateur video posted on YouTube showed a pile of bodies on the floor, and other bodies scattered around as several small fires burned.
The airport was briefly closed to planes immediately after the blast, but soon reopened.
No one immediately claimed responsibility for the explosion. Chechen militants have claimed responsibility for previous terror attacks in Moscow, including a double suicide bombing on the underground in March 2010 that killed 40 people and wounded more than 100.
Large-scale battles in Chechnya ended years ago, following two devastating wars between Russia and the region's separatists, but Islamic militants have continued to carry out suicide bombings and other attacks.
Most have been in Chechnya and other predominantly Muslim provinces in the southern Caucasus region, but some have targeted Moscow, including its underground, buses and trains.
Car rental agent Alexei Spiridonov, 25, was at his desk when the blast struck about 100 yards away.
"The explosion was so strong that it threw me against the wall," he said. "People were panicking, rushing out of the hall or looking for their relatives. There were people just lying in blood."
Yelena Zatserkovnaya, a Lufthansa worker, said she was a similar distance away. "There was lots of blood, severed legs flying around."
Airport workers were using baggage trolleys to cart out the injured, she said.
Sergei Lavochkin, who was waiting in the arrivals hall for a friend to arrive from Cuba, said emergency teams carried people out of the terminal.
"I heard a loud bang, saw plastic panels falling down from the ceiling and heard people screaming. Then people started running away," he said.
Hours after the blast, passengers arriving for their flights lined up outside waiting to pass through metal detectors that had been installed at all entrances. At least 20 ambulances and 10 fire trucks remained outside.
Built in 1964, Domodedovo is 26 miles south-east of the centre of Moscow and is the largest of the three major airports that serve the Russian capital, carrying more than 22 million people last year.