FOUR terrorist bomb blasts at Underground stations and on a London bus rocked the capital this morning, leaving walls spattered with blood and scores of Tube passengers staggering through choking fumes and darkness.

In all at least 33 people have been killed, 21 of them at King's Cross Station, 45 seriously wounded, and more than three hundred left carrying minor injuries.

The entire Tube network was shut down and will probably remain so into Friday.

The rush-hour blasts took place at Edgware Road station, on a bus in Tavistock Square, between Russell Square and King's Cross Tube stations and between Aldgate East and Liverpool Street Tube stations.

Within minutes a City of London police spokesman said there were "quite a large number of casualties".

Walls in Tavistock Square close to the British Medical Association headquarters were splattered with blood where a No.30 bus was left with its upper deck torn to shreds.

Home Secretary Charles Clarke spoke of "terrible injuries" and Prime Minister Tony Blair left the G8 summit in Scotland to head for London.

Met Commissioner Sir Ian Blair said: "We are advising members of the public not to travel into London. Public transport in London will be affected in the next few days."

Like all other stations, Kings Cross station has been evacuated, with its stranded passengers and tourists being accommodated in Camley Street Nature Reserve, which is scheduled to remain open throughout the night.

Police initially declared a "major incident" at Aldgate station at 8.50am and reported further explosions in "multiple locations".

Several casualties were taken to hospital after an explosion at close to Liverpool Street station that emergency services said had been caused by an electrical power surge.

Police are investigating incidents at Edgware Road, Kings Cross, Liverpool Street, Russell Square, Aldgate East and Moorgate Tube stations.

Early reports of two additional bus explosions appear to be unfounded however.

One Tube passenger said: "People started screaming and there was what appeared to be smoke and soot everywhere. It was all over our clothes and our hands. Nobody knew what was going on.

"People started screaming, everyone felt uncomfortable. Some people started grabbing emergency hammers trying to smash windows and open doors. No one had any idea what was going on."

Tube bosses have suspended the entire network and stations have been evacuated.

The leader of the House of Commons, Geoff Hoon, said government ministers were meeting to clarify the situation.