It is understood that he was found not to have been carrying a bomb.

Three officers had followed him to Stockwell station after he emerged from a nearby house that police believed to be connected with Thursday’s attempted bombings.

The suspect, described as being of Asian appearance and wearing a thick, bulky jacket, vaulted over a ticket barrier when challenged by police and ran down the escalator and along the platform of the Northern Line.

When the armed officers reached the platform with their guns drawn, they shouted at everyone to get down. As waiting passengers and those already on a train that had pulled into the station dived to the floor, the suspect jumped on the train. Two witnesses said that as he entered the train he tripped, ending up half in and half out of the carriage, on all fours. Within seconds, as the clock tower outside the station chimed 10am, the officers caught up with the man and pushed him hard to the floor. Witnesses said that they then fired up to five bullets into him at close range, killing him instantly.

Anthony Larkin, 30, was waiting on the platform when he saw a man in a black bomber jacket and jeans running towards him being chased by the officers. Mr Larkin, a care assistant, from Hartlepool, Teesside, said: “The officers were shouting, ‘Get down, get down’. I immediately hit the ground. I saw the man fall over and then I heard two shots that I believe went into his back.

“There was lots of panicking, people ran screaming out of the station and they were keeping their heads down. I just got up and joined them, running as fast as I could.”

Alerted by the bulk of his jacket, police had followed the suspect on foot for some time and became concerned when he approached the Tube station.

After the officers were ordered to stop him from entering the station at all costs, they challenged him before he crossed the main road to the station.

When they drew their weapons and shouted “Stop, armed police”, the man looked over his shoulder and bolted. He was described as being very fit and agile.

After the suspect had been shot police sent a robot to examine the man, because of fears that any device could still prove a danger. But it is understood that no device was found.

Police are describing him as an “intimate accomplice of the cell”. His name and address were thought to have been found among the possessions left by the would-be bombers on Thursday.

Police sources said he did not live at the address from which he had been followed.

Another witness said that the suspect boarded the Tube and attempted to take a hostage before he was shot.

Dan Copeland, a Northern Line passenger, told BBC News: “The man burst in through the carriage door to my right and grabbed hold of the pole and a person by the glass partition near the door, diagonally opposite me.

“An officer jumped on to my left and screamed, ‘Everybody out’. As I turned out of the door on to the platform I heard four dull bangs.”

The Metropolitan Police said that an Independent Police Complaints Commission investigation will begin, which will inevitably focus on some of the witness accounts.

The incident sparked panic among travellers, some of whom were treated for shock and minor injuries.

Within 20 minutes of the shooting, more armed officers from Scotland Yard’s SO19 group ran into the station carrying semi-automatic weapons, witnesses said.

At 10.42am police cordoned off an area around the station and closed off the busy A3, which runs between Central London and the South Coast. Traffic was backed up for miles. At the same time, the Victoria and Northern lines were stopped. They reopened at 12.20pm.

Just before that, Christine Burgess, 56, who was travelling past the station on a bus, said that she saw a body bag being brought out of the station and put into an ambulance.

Early this morning the area was still cordoned off.

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