Shocked survivors told how they saw a "suicide bomber" on board the double-decker bus destroyed in Thursday's terrorist outrage.

Thirteen people were killed when the packed No. 30 was ripped apart by a 9:47 a.m. blast in Tavistock Square (search), Central London.

Witnesses said bodies were thrown into the street from the bus — crammed with commuters forced above ground after the capital's Tube network was shut down.

Terence Mutasa, 27, a staff nurse at University College hospital (search), said: "I treated two girls in their 20s who were involved in the bus bomb.

"They were saying some guy came and sat down and that he exploded. The girls received minor injuries and were in shock and distressed.

"They said the guy just sat down and the explosion happened. They thought it was a suicide bomber."

Passenger Richard Jones was convinced he saw the bomber setting his device.

He said he became suspicious of the olive-skinned man because he looked anxious and was fiddling constantly with his bag.

Richard, 61, said: "I noticed him as he looked nervous. He was continually diving into his bag, rummaging round and looking in it. I did not see his face because he was constantly looking down."

Richard stepped off the bus at his destination. Seconds later it exploded behind him — with the "bomber" still on board.

Jasmine Gardner, 22, was angry at not being allowed on the bus because it was too full — then seconds later saw it blown to bits.

Jasmine, who had angrily followed the bus on foot, put up her umbrella to try to protect herself from flying debris.

She said: "I thought that everyone must have died."

If confirmed as a suicide bombing, the attack would be the first of its kind to take place on British soil.

Passer-by Stephanie Riak Akuei, 44, helped rescue and bandage survivors of the blast, which happened close to the British Medical Association (search) headquarters.

Stephanie, from California, worked with doctors from a BMA conference to tend the injured, using knowledge from a rudimentary first-aid course.

"I was on the corner and heard the noise. I went over and there were at least seven people obviously dead. There was a lot of body parts and human debris. There were people dead, people alive, trapped on the bus.

"At first there was an eerie quiet and a very profuse smell of blood which was consuming. One man began screaming. Another was only visible by his head. When we pulled him out, the bones of his legs were in pieces and the flesh was torn out.

"I think there were at least 20 people on the bus. At least five were beyond recognition and we covered them up with blankets.

"It was very traumatic. Some people who might not survive were crying out. One man called: 'My leg, my leg.' Another was saying 'My eyes' because he couldn't see. Two or three people stopped breathing while I was there."

Onlookers said the bus's roof was blown off "like the lid of a sardine tin." Blood splattered the walls of nearby buildings, staining as high as the second story.

Body parts lay scattered in the middle of the road.

Security guard Ayobami Bello told how he saw dead victims in the street. He said: "It was terrible. The bus went to pieces. There were so many bodies on the floor.

"The back was completely gone, it was blown off and a body was hanging out. Others were on the road."

Mr Bello, 46, — who works at the nearby London School of Tropical Hygiene and Medicine (search) — said other victims sat slumped in their seats, some missing limbs.

Witnesses said the bus, which had been diverted in the emergency and was traveling from Hackney Wick to Marble Arch, was "packed" with people turned away from sealed-off Tube stops.

Belinda Seabrook said: "I was on the bus in front and heard an incredible bang. I turned round and half the double-decker was in the air.

"I knew there must be a lot of people dead as all the buses were packed — they had been turning people away from the Tube stops."

Cabbie Michael Michael, 48, from Cockfosters in North London, saw the bomb explode ahead of him.

He said: "Bam, the top of the bus just ripped up. I heard the sound, and I could see the bus from a distance. The roof went up."

Cycle courier Andrew Childs, 36, said: "The bus was just shredded. There was a cloud of smoke and a bang. The roof was totally ripped off. It was like a shredded pile of metal."

Raj Mattoo, 35, was standing nearby when the bus exploded.

He said: "The blast seemed to be at the back. The roof flew off and went up about ten meters. It then floated back down.

"People were badly injured. A parking attendant said he thought a piece of human flesh landed on his arm."

The blast, just a few hundred yards from Russell Square station, rocked the Tavistock Hotel (search). Some of those killed were passers-by.

But the bus driver escaped with only cuts and bruises.