The blast ripped through baggage claims at the arrivals hall at Russia's largest airport.
A suspected suicide bomber attacked Moscow's Domodedovo international airport.
At least 31 people were killed and 130 wounded in the blast.
The Russian capital has been repeatedly rocked by attacks over the last years blamed on militants from its Northern Caucasus region.
A suspected suicide bombing Monday killed at least 31 people and wounded over 100 at Moscow's Domodedovo international airport in an attack described by investigators as an act of terror.
Eyewitnesses who spoke to Russian radio described a scene of carnage after the blast ripped through the baggage claims section of the arrivals hall at Russia's largest airport.
"Today at 4:32 pm (1332 GMT) an explosion went off in the international arrivals hall of Domodedovo airport," the Russian investigative committee said in a statement.
The spokesman for the committee, Vladimir Markin, said that a criminal inquiry had been opened into an "act of terror".
An official with the investigators, Tatyana Morozova, told the Interfax news agency that the blast happened in the baggage claim area.
At least 31 people were killed and 130 wounded in the blast, Interfax said, quoting an official with the health ministry.
"According to preliminary information, the explosive device was set off by a suicide bomber in the international departures hall," the news agency quoted an unnamed security source as saying.
"Burned people are running about. ... They are carrying pieces of flesh on stretchers," said one eyewitness, named as Andrei, who was standing near the information stand at the airport.
"Something terrible is happening there. Tens of people are being dragged out on stretchers, on trolleys," he told City FM radio.
"People are on stretchers, some being carried, there are wounded, people covered in blood," a passenger named as Nadezhda told the radio.
"You can't tell the living from the dead. I was meeting someone. We are not protected in this country," another witness, Alexei, told the radio.
Prime Minister Vladimir Putin has been informed of the incident, his spokesman Dmitry Peskov told Interfax.
Moscow police on Monday stepped up security across the city after the blast, Interfax quoted law enforcement officials as saying.
Domodedovo Airport is Russia's largest airport in terms of passenger traffic.
The Russian capital has been repeatedly rocked by attacks over the last years blamed on militants from its overwhelmingly Muslim Northern Caucasus region.
Double bombings carried out by two female suicide bombers on the Moscow metro on March 29, 2010 killed 40 and wounded more than 100.
Russia is battling an Islamist insurgency in the Caucasus and deadly attacks on government and police officials in Dagestan as well as neighboring Chechnya and Ingushetia are an almost daily occurrence.
The Kremlin fought two wars against separatist rebels in Chechnya in the 1990s but the insurgency has now become more Islamist in tone and has spread to neighboring Ingushetia and Dagestan.
However officials have repeatedly warned of the risk of attacks in Russia's heartland.