In comments broadcast on national television, Medvedev demanded answers from Domodedovo airport over how it let the bomber wander into arrivals and set off a charge just as passengers from several international flights were arriving.

The blast represented a major setback for Russia's international image and confidence in its security as it gears up to hold two major sporting events: the Winter Olympics in 2014 and the 2018 World Cup.

Sources told the state-run RIA Novosti news agency that the attack bore all the hallmarks of militants from the overwhelmingly Muslim Caucasus region who have behind a string of attacks in the Russian capital over the last years.

The bomber may have been a woman, the agency said, although initial reports had said it was a man in his 30s.

The blast, which caused caused carnage at Domodedovo, put the country on high alert and saw Russia receive an outpouring of support from Western capitals as well as the United Nations and NATO.

"Based on (the bomb's) location and other indirect evidence, this was a well-planed act of terror that aimed to kill as many people as possible," Medvedev said.

But the Kremlin chief faulted airport security and said that Domodedovo's executives would be held accountable for lapses that facilitated the attack.

"What happened demonstrates that there were clear security breaches. Someone had to try very hard to carry or bring through such a vast amount of explosives," Medvedev said.

Initial reports said the blast had the force of between five and seven kilogrammes (11 and 15.4 pounds) of TNT.

"Everyone linked to the company that makes decisions there, and the management of the airport itself, has to answer for everything. This is an act of terror. This is grief. This is a tragedy," the president said.

An airport spokeswoman said that all the security procedures had been followed correctly and Domodedovo was not to blame.

"We do not feel that we should be held accountable," Yelena Galanova told Interfax.

Moscow's second devastating attack in less than a year prompted immediate speculation that the blast was linked to the continued turbulence in Russia's predominantly Muslim North Caucasus region.

"The explosion occurred the moment the presumed female suicide bomber opened her bag," the RIA Novosti agency quoted the unnamed security official as saying.

"The terrorist was accompanied by a man. He was standing beside her and (the blast) tore off his head."

Russian investigators said Monday they had found a head of "Arab appearance" that was initially presumed to have belonged to the suicide bomber.

"This act of terror followed the classic scheme used by terrorists who come from the North Caucasus," said the security official.

Some newspapers reports suggested that the attack may have been planned since the New Year's Eve -- the date a bomb went off under mysterious circumstances in a small building on the site of a Moscow sports club.

There were scenes of carnage Monday as corpses were stretchered out of the smoke-filled arrivals area after the blast.

Survivors -- some of them splattered in blood -- said people were torn to pieces from a bomb that appeared to be filled with nuts and bolts.

The emergencies ministry said in a statement Tuesday that the updated list of people in hospital had gone up to 108.

The attack struck a recently renovated airport that handles major international traffic routes and had just received flights from British Airways and BMI.

Initials reports said that at least one Britain had died. The list of those injured also included one man from Italy and another from France as well a Serb national and Zuzana Fialova -- an actress from Slovakia.

Prime Minister Vladimir Putin -- who spearheaded Russia's campaigns for the right to host both events -- has said little about the incident accept for issuing instructions concerning medical assistance and other help.

But the bombing drew an instant response from global leaders. US President Barack Obama called the attack "outrageous" while German Chancellor Angela Merkel described it as "cowardly".

Chinese President Hu Jintao sent a message to Medvedev saying that his country "condemns terrorist attacks of any kind and resolutely supports Russian measures to fight terror."

The Russian capital has been repeatedly rocked by attacks over the last years blamed on militants from the predominantly Muslim Northern Caucasus.

Double bombings carried out by two female suicide bombers on the Moscow metro on March 29, 2010 killed 40 and wounded more than 100.