It was during the height of morning rush hour Thursday that four bombs ripped apart three trains on London's Underground transit system and a double-decker bus. (Timeline (http://edition.cnn.com/2005/WORLD/europe/07/07/london.timeline/index.html))
Authorities were at work at all the bomb sites except the one beneath Russell Square station, where at least 21 people died, which must be made safe before police work can begin in earnest.
There are fears about the stability of the tunnel, "vermin and other dangerous substances," according to Deputy Police Commissioner Andy Hayman, who's heading the investigation.
The Tavistock Place site, where a bomb killed 13 people aboard a bus, was also challenging, because the explosion took place in the open air, spreading debris over a wide area, he said. All bodies from that site have been recovered, Police Commissioner Ian Blair said.
Seven people died in each of the other two Underground bombings, which occurred near the Edgware Road and Liverpool Street stations. One person died in the hospital.
Half of the 700 wounded were treated on the scene, and the rest were taken to hospitals, Blair said. Of the wounded, 100 people remained in hospitals overnight; 22 suffer from serious injuries.
Blair said the total death toll from the attacks would rise, but not above 100.
As a massive manhunt got under way Friday, Blair said the attacks had "all the hallmarks of al Qaeda."
He said that while the investigation was in very early stages, no evidence had been found of suicide bombers or timing devices. (Read more)
The bombs used in the attacks held less than 10 pounds of explosives each -- light enough to easily tote in a bag or knapsack, police said.
"The most important statement I can make," Blair said, "is the implacable resolve of the Metropolitan Police Service to track those who are responsible for these terrible events."
He defended a decision to relax Britain's alert level in recent months and said there were no warnings ahead of the blasts.
"There is nothing to suggest that intelligence has been missed in any way," he said.
Earlier Friday, Britain's top law enforcement official said police were searching for the bombers before they had a chance to strike again. (CCTV clues)
"We have to have ... maximum consideration of the risk of another attack, and that's why our total effort today is focused on identifying the perpetrators and bringing them to justice," Home Secretary Charles Clarke told BBC radio.
"The fact is, we're looking for a very small number of very evil needles in a very large haystack, which is the city of London," Clarke said.
He said the government was taking seriously a claim of responsibility on the Internet from a group calling itself "The Group of al Qaeda of Jihad Organization in Europe." The authenticity of the claim could not be verified.
London Mayor Ken Livingstone said the attack was not related to Britain's participation in the U.S.-led invasion of Iraq. London, he said, is a symbol of the lifestyle terrorists despise, particularly its multicultural heritage.
Livingstone also praised the authorities' rapid responses, saying, "Everything that we had planned for this day we knew would come worked like clockwork."
He just returned from Singapore, where an announcement that London will host the 2012 Olympic Games inspired celebrations back home a day before the attacks.
Meanwhile, relatives and friends of people missing since the attacks feared the worst after hearing nothing from their loved ones for more than 24 hours.
Missing persons posters were going up around London and being handed out in a frantic hunt for information, the UK's Press Association reported.
Among the missing was Jamie Gordon, a 30-year-old worker in London's financial district, his girlfriend Yvonne Nash told PA.
Nash said she feared Gordon was on the No. 30 bus that was destroyed, and his colleagues have been searching the streets of London and putting up posters of him.
"We just don't know where he is and we are just desperate to find out. We are just trying to keep going. Is he dead? Is he alive? Not knowing is dreadful," she told PA.
Also missing is Laura Webb, 29, who would have been taking a train from King's Cross to Paddington, her boyfriend Chris Driver said.
"I just hope she may have knocked her head or something like that, and that she is somewhere being looked after," Driver told PA.
"We are very upset about her disappearance, and all the options go through your mind," Webb's brother David said.
Most bus and some Underground services had been restored by Friday, but police were urging people not to come into the British capital unless necessary.
Traffic was lighter than normal, with many Tube stations, buses and road nearly empty. Those who did venture into trains and buses said they had little choice.
"I was scared, but what can you do?" Raj Varatharaj, 32, told AP as he emerged from an Underground station. "This is the fastest way for me to get to work. You just have to carry on."
Bus route No. 30 was full of commuters Friday morning, despite the previous day's blast that tore through a bus on the same route. Large screens were erected to shield the wreckage of the bus from onlookers. (Full story) (http://edition.cnn.com/2005/WORLD/europe/07/08/passengers.return/index.html/)
Meanwhile, British newspapers marked London's bloodiest peacetime attack with somber front pages that struck a defiant tone. (Press review)
In Britain and across the world, Arabs and Muslims expressed outrage at the terrorist attacks, with the dominant viewpoint summed up by one person who wrote on a Web site, "Enough ... enough." (Arab, Muslim reaction) (http://edition.cnn.com/2005/WORLD/europe/07/08/london.muslims/index.html/)
Stocks closed higher in Europe Friday, regaining some of the ground they lost Thursday. (Europe stocks)
And Queen Elizabeth II visited some of the wounded at Royal London Hospital, where she said the terrorists "will not change our way of life."(Royal response) (http://edition.cnn.com/2005/WORLD/europe/07/08/london.attacks//)
Shortly after returning to Washington from the G8 summit in Scotland, President Bush signed a condolence book Friday at the British Embassy and offered his sympathy to British Ambassador David Manning and the British people:
"Yesterday was an incredibly sad day for a lot of families in London. It's my honor, ambassador, to come and represent our great country in extending our condolences to the people of Great Britain. To those who suffered loss of life, we pray for God's blessings. For those who are injured, we pray for fast healing. British people are steadfast and strong. We've long admired the great spirit of Londoners and the people of Great Britain. Once again, that great strength of character is coming through."
Earlier, Prime Minister Tony Blair closed the summit Friday, saying, "We speak today in the shadow of terrorism, but it will not obscure what we came here to achieve. (G8 summit; Special report (http://edition.cnn.com/SPECIALS/2005/g8/))
The G8 leaders issued a joint statement in the wake of the attacks.