Police today shot and killed a suspect after a chase to the doorway of a London Tube train.
The Metropolitan Police Commssioner, Sir Ian Blair, said the shooting at Stockwell station in south London was linked directly to the "ongoing and expanding" operation in the wake of yesterday's attacks across the capital.
He said: "This man was challenged and refused to obey police instructions."
Sir Ian appealed for calm, saying that police needed the understanding and co-operation of all communities. He added: "We know there are rumours sweeping London and I appeal to everyone to listen to the facts.".
Meanwhile anti-terrorist officers released four CCTV images of men they wanted to interview in connection with yesterday's attacks. They included one of a running man at Oval station, scene of one of yesterday's attacks. The man, wearing a top with New York on it in large letters, was said to have boarded a train at Stockwell, but police said he was not the same man as the one shot at that station today.
Earlier, passengers evacuated from Stockwell station during this morning's shooting described seeing armed police chasing a suspect before opening fire.
Passenger Mark Whitby, speaking to BBC News 24, reported the man was shot five times at close range after he had jumped on a train at Stockwell. He had been sitting on the train reading his paper as it was stationary with its doors open in Stockwell station when he heard people shouting "get down, get down!"
He said that Asian man ran on to the train pursued by three plainclothes police officers.
He said the man tripped and was also pushed to the floor. He said: "One of the police officers was holding a black automatic pistol in his left hand. They held it down to him and unloaded five shots into him. I saw it. He's dead, five shots, he's dead."
He reported the man did not seem to be carrying a weapon or wearing a rucksack.
Passenger Briony Coetsee, 23, said: "We were on the Tube when we suddenly heard someone say 'get out, get out' and then we heard gunshots - someone was shooting.
"Somebody in plain clothes who I thought was a civilian cop had his gun out and started shooting and told us to get out."
Chris Wells, a 28-year-old company manager, said he was travelling on the Victoria Line towards Vauxhall when he left the train at Stockwell.
He saw about 20 police officers, some of them armed, rushing into the station before a man jumped over the barriers with police giving chase.
He said: "There were at least 20 of them (officers) and they were carrying big black guns.
"The next thing I saw was this guy jump over the barriers and the police officers were chasing after him and everyone was just shouting 'get out, get out"'.
Christopher Scaglione, 35, a fashion designer, was also on a Victoria Line tube train shortly before the incident.
He said: "The train didn't stop at Vauxhall and so I got out at Stockwell. I was just on my way out when I heard at first a little bang, not like a bomb more like a gun, and then people were shouting. People then started to run and I heard two or three more bangs like people shooting."
A large area around Stockwell Tube Station, an interchange for the Northern and Victoria lines in south London, was cordoned off and traffic approaching the area ground to a halt.
* A major police operation was reported at Harrow Road, near Paddington, where bomb disposal officers were deployed an address in West Kilburn. A resident of Portnall Road, just off Harrow Road, told the BBC: "From my windown I can see 20 doors down what looks like a bomb disposal type vehicle, it's armoured and there are several armed officers around it. About half an hour ago officers the police ran up my road telling everyone to get inside their houses."Reuse content