At least 38 people have been killed and hundreds injured in a series of explosions across London. The BBC News website is covering events as they unfold (all times in BST):
2341 Police re-open the majority of the roads previously closed by cordons in central London. But cordons remain in place in Woburn Place, Tavistock Place, Burton Street and Flaxman Terrace.
2105 UK Prime Minister Tony Blair arrives back in Gleneagles,
Scotland to rejoin the G8 summit.
1947 Buckingham Palace says that Queen Elizabeth II will visit some of those caught up in the London attacks on Friday.
1940 The UK foreign secretary, Jack Straw, says the London attacks bear all the hallmarks of al-Qaeda. Mr Straw, who has temporarily taken over as chairman of the G8 summit in Scotland, said neither the British police nor the intelligence services had any warning of the attacks.
1816 US Secretary of State Condoleezza Rice orders US embassies across the globe to review their security posture in the wake of the London attacks, the US State Department says.
1813 The number of people confirmed dead in the London bomb attacks has risen to 37, Deputy Assistant Police Commissioner Brian Paddick says. Twenty-one were killed at Kings Cross/Russell Square, seven died at Edgware Road, seven died at Liverpool Street and two died on the bus at Upper Woburn Place. A further 700 were injured, 300 of whom were taken to various London hospitals by ambulance.
1753 The UN Security Council unanimously passes a resolution condemning the London attacks, saying it regards any act of terrorism as "a threat to peace and security".
1732 UK Prime Minister Tony Blair promises the "most intense" police and security forces action to bring those who carried out the London attacks to justice. He says the terrorists "act in the name of Islam" but he knows most Muslims worldwide "deplore this act of terrorism". He insists that in the face of these attacks the British people remain resolute: "It is a very sad day for the British people but we will hold true to the British way of life."
1657 All major West End theatre productions are cancelled for tonight - something which has not happened since World War II, apart from on the days of state funerals.
1653 The Union Jack flag will be flown at half mast on all UK government buildings tomorrow, a Department for Culture spokesman says.
0851 Seven people die in a blast on a train 100 yards from Liverpool Street station
0856 21 people die in a blast on a train between Russell Square and King's Cross stations
0917 Five people die in blast on a train at Edgware Road station
0947 An unknown number die in a blast on a bus at Tavistock Place.
1635 The Union Jack flag flying over Buckingham Palace is lowered to half mast at Queen Elizabeth II's request.
1609 London transport officials report that all tube lines in the city remain closed, although it is hoped some of the lines unaffected by the blasts will reopen on Friday. All main overland train stations apart from Kings Cross and Victoria are now open. It is hoped that bus services will resume in central London later this afternoon.
1603 Scotland Yard issues a casualty hotline number for people worried about their relatives. The number is 0870 1566 344.
1555 US raises its terror alert level for rail and subway systems, but not for airlines, officials say.
1546 London police say there have been no arrests in connection with the blasts so far and that they are "keeping an open mind as to who the perpetrators might be".
1533 London ambulance service reports that 45 people were seriously injured in the blasts, sustaining injuries such as severe burns, amputations, chest and blast injuries. A further 300 sustained minor injuries, such as lacerations and smoke inhalation. All injured have been removed from the bombed vehicles they say.
1525 Police confirm that at 33 people have been killed in the London blasts. At least seven were killed in an explosion on a tube train near Aldgate East station. At least another 21 were killed in an explosion on a tube train in the Kings Cross/Russell Square area. Five have been confirmed killed in the Edgware Road station blast and there were fatalities on the bus attacked near Woburn Square, although how many is not yet known.
1510 UK Prime Minister Tony Blair arrives back in Downing Street.
1505 The former mayor of New York, Rudolph Giuliani, describes the explosions as "dastardly, cowardly acts". "My heart goes out to the people who were affected by this, it reminds me so much of 11 September," Mr Giuliani, who is visiting London at the moment and was near Liverpool Street station as the first blast hit, said.
1458 Sir Iqbal Sacranie, the Secretary General of the Muslim Council of Britain, joins other religious leaders in condemning the attacks, saying "as with all other people in the community, we totally condemn the perpetrators of what appears to be this series of co-ordinated attacks in London which tragically has led to several fatalities and a large number of casualties".
1418 A Transport for London spokeswoman says the bus hit by the explosion was a number 30, travelling from Hackney to Marble Arch.
1353 Russian President Vladimir Putin expresses his condolences over the attacks and calls on all countries to unite in the fight against international terrorism.
1344 The Archbishop of Canterbury, Dr Rowan Williams, describes the attacks as appalling and calls on all religious leaders to stand and work together for the wellbeing of the nation.
1333 US President George W Bush, speaking at the Gleneagles summit in Scotland, condemns the attacks, saying that the blasts show the war on terror must continue.
1325 UK Prime Minister Tony Blair leaves Gleneagles summit in Chinook helicopter.
1313 The Mayor of London, Ken Livingstone, condemns a "cowardly terrorist attack" and says Londoners responded "calmly and courageously".
1307 G8 leaders issue a statement, read by Tony Blair, saying: "We condemn utterly these barbaric attacks."
1255 Home Secretary Charles Clarke tells the House of Commons that four explosions had been confirmed, three on trains and a fourth on a bus. "We do not know who or what organisations are responsible for these terrible criminal acts," he says. He says the Underground will remain closed all day.
Shadow home secretary David Davis says the attacks are "of almost unspeakable depravity and wickedness". Liberal Democrat spokesman Sir Menzies Campbell expresses sympathy to those affected and appreciation to the emergency services.
1246 Pope Benedict XVI condemns the "inhuman" attacks.
1215 The ambulance service says there are people still trapped at King's Cross station, and efforts are being made to rescue them.
1210 The BBC's Security Correspondent Frank Gardner says BBC monitoring services have located a website linked to al-Qaeda with a 200-word statement saying it carried out the bombings.
1205 Prime Minister Tony Blair, at the G8 summit in Gleneagles, says there has been "a series of terrorist attacks in London... people have died and are seriously injured... It is reasonably clear this is designed and timed to coincide with the opening of the G8". He says he will return to London within hours, but that the summit will continue without him.
LOCATIONS EMERGENCY SERVICES WERE CALLED TO
1205 The Bishop of London, Richard Chartres, said: "This is a grave day for London. Our thoughts and prayers are with the injured and bereaved."
1130 Signs on major roads into London warn: "Avoid London. Area closed. Turn on radio."
1126 The president of the European Parliament, Josep Borrell, blames terrorism for a "co-ordinated series of attacks" and "confirmed deaths".
1125 "We have at least two fatalities, but still unconfirmed," a police spokesman tells the AFP news agency.
1118 London's Metropolitan Police Commissioner Sir Ian Blair tells the BBC he knows of "about six explosions", one on a bus and the others related to Underground stations. He says he believes the six affected areas are Edgware Road, King's Cross, Liverpool Street, Russell Square, Aldgate East and Moorgate, but says it is "still a confusing situation". He advises Londoners to "stay where you are - all of London's transport is currently disabled" - he refuses to confirm any fatalities.
1055 A doctor tells Reuters there are at least 90 casualties at Aldgate station.
1053 Home Secretary Charles Clarke makes a statement outside Downing Street about "dreadful incidents" causing "terrible injuries". He says Prime Minister Tony Blair has been informed and advises the public in London not to make unnecessary journeys.
1051 A passenger on a train at Edgware Road says he saw several bodies in the wreckage. A police spokesman says two trains remain stuck in tunnels at Edgware Road.
1049 Police say there are serious casualties, but no deaths are confirmed, Associated Press reports.
1039 All London hospitals have been put on major incident alert, a hospital spokesman tells PA.
1025 Transport union officials say they have reports of explosions on three buses, PA says.
1025 PA reports two buses damaged in explosions - one in Russell Square and another in Tavistock Square. Witness, Belinda Seabrook said of the Russell Square blast: "I was on the bus in front and heard an incredible bang, I turned round and half the double decker bus was in the air."
1025 The BBC's Andrew Marr, with the prime minister in Gleneagles, says Number 10 is "still unsure" whether the explosions are a terrorist attack.
1023 British Transport Police confirm an explosion on a bus in Tavistock Square.
1021 Scotland Yard reports "multiple explosions" in London, the Press Association reports.
1014 An eyewitness tells PA that a bus has been ripped apart in an explosion in central London.
1009 Witness Christina Lawrence, who was on a train leaving Kings Cross, tells BBC News 24: "There was a loud bang in the tunnel and the train just stopped and all of a sudden it was filled with black, gassy smoke and we couldn't breathe."
1002 Scotland Yard says it is dealing with a "major incident".
0940 British Transport Police say power surge incidents have occurred on the Underground at Aldgate, Edgware Road, King's Cross, Old Street and Russell Square stations.
0933 London Underground reports "another incident at Edgware Road" station, PA reports.
0933 Passengers are told that all London Underground services are being suspended because of a power fault across the network, PA reports.
0924 British Transport Police say the incident was possibly caused by a collision between two trains, a power cut or a power cable exploding. Police report "walking wounded".
0915 Press Association reports emergency services called to London's Liverpool Street Station after reports of an explosion.
0849 An incident on the Metropolitan Line between Liverpool Street and Aldgate is reported to British Transport Police.