At least 35 people, including two Britons, were killed Monday after a suspected suicide bomber blew himself up at Moscow's busiest airport.

The bomber entered the ground floor of Domodedovo airport's terminal building apparently unchallenged. He then made his way to the crowded international arrivals zone. At 4:32 p.m. local time he set off a massive explosive device, possibly hidden in a suitcase, causing a blast equivalent to 7 kilograms (about 16 lbs.) of TNT.

Up to 168 people were injured, many of them critically. Relatives waiting to meet family members and arriving passengers were killed instantly.

Witness Artyom Zhilenkov, 30, survived the blast and tonight told the Guardian newspaper: "There was a massive boom and then a wave of heat and pressure that swept along the floor, bent my legs and flung me aside.

"I was looking toward a dark-skinned man when it happened. I think it was the suitcase standing next to him that exploded."

According to unconfirmed reports, investigators found the head of a man aged 30 to 35, who is thought to be the suicide bomber.

Video footage from the airport showed bodies seemingly piled in a heap, fires burning, and abandoned luggage. Rescuers were shouting through the smoke. Some of the wounded were transported to ambulances on baggage trolleys.