The four coordinated explosions hit London commuter routes in the middle of morning rush hour, killing dozens of people and wounding hundreds more. In the aftermath, rescue workers, police and ordinary people streamed into blood-splattered streets to help. Buses ferried the wounded. Medics used a hotel as a hospital.

The first subway blast hit at 8:51 a.m., the others at 8:56 a.m. and 9:17 a.m. The bus exploded a half-hour later.

Passengers emerged from the London Underground covered with blood and soot.

"People were running everywhere and screaming," said Gary Lewis, 32, who was evacuated from King's Cross, the worst-hit station, where at least 22 people died. "The one haunting image was someone whose face was totally black and pouring with blood."

Near central London's Russell Square, the bus's mangled upper deck was open to the sky. Doctors from the nearby British Medical Association rushed outside to treat the wounded.

"The most extreme thing I first noticed was that there was someone in bits in the road," said Dr. Laurence Buckman. "The front of BMA house was completely splattered with blood and not much of the bus was left."

Reporters and TV crews pressed against police tape at the scene. Behind them, passers-by held cell phones in the air to take pictures or video of the wreckage.

Raj Mattoo, 35, said the explosion seemed to occur at the back of the bus. "The roof flew off and went up about (30 feet). It then floated back down."

Just a day before, London basked in the glory of winning the 2012 Olympic Games, with wild celebrations on Trafalgar Square. Now, the Union Jack at Buckingham Palace flew at half-staff in respect for the dead and injured.

An eerie quiet took hold in parts of the city.

Police went on emergency alert code amber as soon as they understood what was happening, shutting down all subways and buses and evacuating passengers, said Brian Paddick of London Metro Police.

Buses became ambulances, carrying dozens of casualties to hospitals. Specialist emergency workers in orange biochemical suits searched the blast scenes for evidence of biological, chemical or nuclear agents.

"There was an explosion and the flash of flames down the side of the train," said Derek Price, 55, who was on a subway near Liverpool Street station, close to one of the blasts. "It was all very quick — a loud bang happened in a matter of seconds."

At the London Hospital, a medic pumped the chest of a man who lay on a stretcher, clothes ripped and body blackened. Medics tended to wounded at King's Cross in the station ticket hall. Emergency workers set up a medical command post in a Hilton hotel near Edgware Road subway station, scene of the third attack.

"One gentleman told me that the floor of the train he was on was blown out, it was just gone," said American Sean Barron, 20, who said he helped treat the wounded at Edgware. "I believe another gentleman was ejected from the train."

Simon Corvett, 26, on a train from Edgware Road station, described "this massive huge bang ... It was absolutely deafening and all the windows shattered."

"You could see the carriage opposite was completely gutted," he said. "There were some people in real trouble."

A Swedish woman who was also riding toward Edgware said she heard the blast behind her train. "Everything went black, and people threw themselves to the floor in panic," Cornelia Berg told Swedish newspaper Aftonbladet by phone.

"The car quickly filled with smoke and a lot of people used their umbrellas to try to break the windows so that we could get air. A mother with her two small children sat next to me and cried desperately."

When passengers left the train, she said, they saw body parts scattered around the station.