More than 33 people were killed in a series of terrorist blasts in London today, police said.
Seven people died in the first blast in a Tube tunnel 100yds from Liverpool Street Station, 21 died in a blast at between King's Cross and Russell Square and five died at Edgware Road station in an explosion involving three trains.
There were also deaths in a bus blast in Upper Woburn Square but no figures are available, Deputy Assistant Commissioner Brian Paddick said.
Mr Paddick said no warnings were given and no claims of responsibility have been received by the police.
The co-ordinated blasts which happened over the space of 60 minutes in the rush hour were condemned by Tony Blair as "barbaric".
The terrorist onslaught was unleashed on the day that G8 world leaders met at Gleneagles.
A group calling itself the Secret Organization Group of al Qaida of Jihad Organization in Europe claimed responsibility for the attacks on an Islamic website.
The message said: "O nation of Islam and nation of Arabism: Rejoice for it is time to take revenge from the British Zionist Crusader Government in retaliation for the massacres Britain is committing in Iraq and Afghanistan.
"The heroic mujahidin have carried out a blessed raid in London. Britain is now burning with fear, terror, and panic in its northern, southern, eastern, and western quarters."
The outrage echoed the al Qaida assault on Madrid commuters in 2004 in which almost 200 people died.
In the wake of the London attacks, survivors gave harrowing accounts of the carnage, describing piles of bodies on wrecked Tube trains and a bus which was torn to pieces along with its passengers.
The day of death and chaos prompted the Prime Minister to vow that the terrorists would never win.
"Whatever they do it is our determination that they will never succeed in destroying what we hold dear in this country and other civilised nations in the world," he said.
Mr Blair left the G8 gathering for London in the wake of the attacks, but said the summit would go on.
Before he left, the G8 leaders appeared side-by-side with Mr Blair to condemn the "barbaric" attacks.
As the scale of the attack became clear, ministers attending the regular Thursday cabinet meeting convened an emergency Cobra committee to deal with the crisis.
The terror attacks began at 8.51am when the bomb exploded in the tunnel near Liverpool Street station, killing seven.
At 8.56am, 21 people died in a blast in a tunnel between King's Cross and Russell Square.
At 9.17am, five people died when a blast ripped through a tunnel wall at Edgware Road station, damaging three trains.
Exactly 30 minutes later at 9.47am a blast tore the roof off the red number 30 double decker bus, packed with commuters forced above ground after the Tube network had been shut down.
Police have not yet released the number of fatalities but eyewitnesses spoke of carnage at the scene.
Two hours later paramedics were still rushing to the scene of the King's Cross blast deep underground on the Piccadilly line.
At Liverpool Street Station in the City, the wounded were treated by medics as they lay on the concourse.
It was the same at King's Cross while the Hilton Metropole on the Edgware Road was used as a makeshift treatment centre.
The bus blast occurred only a few hundred yards from Russell Square station.
London was thrown into chaos in the wake of the blasts with shops, banks and offices closing and thousands of people left stranded on the streets as mainline stations were shut and Tube and bus services cancelled.
Metropolitan Police Commissioner Sir Ian Blair said there was evidence of explosives at at least one of the explosion sites.
Police said it was too early to say whether they had been caused by planted explosive devices, or whether they were the work of suicide bombers.
The blasts were initially blamed on a power surge but it soon became clear that it was a co-ordinated terrorist attack on the capital.
The G8 gathering had prompted fears of a terrorist spectacular.
Home Secretary Charles Clarke told a sombre House of Commons the blasts were "criminal and appalling acts".
Speaking at Gleneagles, US President George Bush vowed that the terrorists would be brought to justice.
The Queen spoke of her shock at the "dreadful events in London this morning".
Respect MP George Galloway said Londoners had "paid the price" for Tony Blair's decision to go to war in Iraq and Afghanistan.
He called on the Prime Minister to withdraw the British troops from Iraq in order to remove people in the UK from "harm's way".
All London hospitals were put on major incident alert after the explosions. Neighbouring counties also sent emergency aid to London.
Metropolitan Police officers in Scotland for the G8 summit were urgently redeployed to London.
Commissioner Sir Ian Blair said: "There is no doubt it is a terrorist incident."
He said the bomb which ripped through the bus in Tavistock Square had exploded in the "back of the upper part of the bus".
He refused to confirm or deny reports that the explosion was the work of a suicide bomber.
An eyewitness described seeing dead bodies lying in the street after the bus bomb.
The security guard at the nearby London School of Tropical Hygiene and Medicine said the blast completely blew the bus apart.
Mr Ayobami Bello, 46, said he had visited a bank nearby and was only 30 metres from the bus when it exploded.
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 completely and a dead body was hanging out and there were dead bodies on the road, it was a horrible thing."
He said other bodies sat slumped in their bus seats, some with arms and legs missing.
He said: "I can't believe it, I can't even believe I survived it.
"There was panic and everyone was running for their lives. I saw a lady coming towards me soaked in blood. Everyone was in confusion."
Survivors of the Tube blasts described scenes of total chaos.
Simon Corvett, 26, from Oxford, was on the eastbound train leaving Edgware Road Tube station when the explosion happened.
He said: "All of sudden there was this massive huge bang. It was absolutely deafening and all the windows shattered.
"The glass did not actually fall out of the windows, it just cracked.
"The train came to a grinding halt, everyone fell off their seats."
Mr Corvett, who works in public relations, said the commuter train was absolutely packed.
"There were just loads of people screaming and the carriages filled with smoke," he said.
"You couldn't really breathe and you couldn't see what was happening. The driver came on the Tannoy and said 'We have got a problem, don't panic'."
Mr Corvett, whose face was covered in soot, joined other passengers to force open the train doors with a fire extinguisher.
He said the carriage on the other track was destroyed.
"You could see the carriage opposite was completely gutted," he added.
"There were some people in real trouble."
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