A suicide bomber walked into the international arrivals area at Moscow's Domodedovo airport Monday afternoon and set off an explosion that killed at least 35 people, including two British travellers.

The blast ripped through a loosely guarded area of the terminal at 4:32 p.m. local time, covering it with thick smoke and shrapnel. More than 180 people were injured.

While no one immediately claimed responsibility for the blast, suspicions turned to militants from the North Caucasus, a region still in the grip of a bitter Islamist insurgency.

"Attempts were being made to identify" the suspected male suicide bomber, Investigative Committee spokesman Vladimir Markin said, adding that the attacker appeared to have been wearing the explosives in a belt. People were sprayed with shrapnel of screws and ball bearings, intended to cause as many casualties as possible.

The Interfax news agency said the head of the suspected bomber had been found.

Markin said two British citizens were among the dead, but they weren't immediately identified.

President Dmitry Medvedev immediately ordered authorities to beef up security at Moscow's two other commercial airports and other key transport facilities. He also cancelled plans to fly out Tuesday to Davos, Switzerland, where he was going to promote Russia as a safe, profitable investment haven to world business leaders.

Monday's attack was expected to strengthen the position of the security forces that form part of Prime Minister Vladimir Putin's base. Large-scale battles in Chechnya ended years ago, after two devastating wars that Russia waged with the republic'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 Caucasus region, but some have targeted Moscow, including its subways, trains and even a theatre.

Ben, an Australian businessman who didn't want his last name used, told CBC Radio's As It Happens Monday night that he heard the explosion while waiting in the immigration line at the terminal. He was about 100 metres away, he said, and blocked by a wall.

He and a Russian-speaking person with him heard no immediate announcement after the blast, but when they got through to customs, they could see the results.

There were baggage carts "loaded with people — injured people and dead people," he said. Two cleaning staff were following the carts, "cleaning up the blood that was flowing from the dead and the injured."

At the same time, Ben said, the airport appeared to be continuing to operate. "It was still a very busy airport." He and his colleague were able to exit the building and get transportation into the city.

Yelena Zatserkovnaya, a Lufthansa official, was also about 100 metres away from the blast site.

"There was lots of blood, severed legs flying around," she said.

Airport workers used baggage trolleys to cart out the injured, she said.

The Russkaya Sluzhba Novostei radio station cited a traveller, identified as Viktor, as saying he heard the 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!"'

Moscow-based freelance reporter Kevin O'Flynn told CBC News that city ambulances and emergency crews rushed to the scene to deal with the injured.

"They were evacuating the rest of the airport without trying to cause a panic," he said.

There were no reports of any Canadian citizens being involved in the blast, Foreign Affairs Minister Lawrence Cannon said in a statement.

"Canada is shocked and deeply concerned by the reports of the explosion at Moscow's Domodedovo airport," Cannon said. "Our thoughts and prayers are with the families affected and the Russian people during this time.

"We condemn these cowardly acts of terrorism."

Cannon said officials at Foreign Affairs are closely following the developments in Moscow.

In Washington Monday, U.S. President Barack Obama condemned the "outrageous act of terrorism" and offered any assistance.

Those comments were echoed by British Prime Minister David Cameron, who spoke with Medvedev and assured him of his complete support.

Eurocontrol, the European air traffic control agency in Brussels, said Domodedovo was briefly closed to air traffic immediately after the blast, but soon reopened.

In 2004, two suicide bombers were able to board planes at Domodedovo by buying tickets illegally from airport personnel. The female 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 subway last March killed 39 people and wounded more than 60.

In December 2009, Chechen rebels claimed responsibility for blowing up a high-speed train between Moscow and St. Petersburg, in an attack that killed 26 people and injured scores.

With files from The Associated Press and the CBC's Margaret Evans