'Multiple' casualties in London after van and knife incident
There are reports of "multiple" casualties following a major incident on London Bridge, British Transport Police said.
Nick Brandon of the BTP's force control room said he had received reports of an incident possibly involving a knife and a vehicle.
The seriousness of the injuries is not yet known, he said.
He said trains were not stopping at London Bridge and Borough Market.
Police are also responding to an incident at Borough Market, Scotland Yard said.
Armed police were at both scenes, the force added.
A BBC reporter at the scene said that police were searching for three suspects and there are multiple reports of witnesses hearing gunfire.
Holly Jones, a BBC reporter at London Bridge when the incident happened, said a van had swerved off the road into a crowd of pedestrians.
"A white van driver came speeding - probably about 50mph - veered of the road into the crowds of people who were walking along the pavement," she told BBC News.
"He swerved right round me and then hit about five or six people. He hit about two people in front of me and then three behind.
I'd say there are about four severely injured people. They all have paramedics assisting them at the moment."
Ms Jones said police were on the scene within two minutes, quickly followed by ambulances.
Police boats were searching the river - apparently looking for people who may have been thrown off the bridge.
She said that among the injured was a French woman who told her she did not know where the two people who had been with her were.
"She told me in French, 'I don't know where those two other people are'. So the police checking the Thames," Ms Jones said.
"They were right near the edge of the bridge. It looks potentially they could have been thrown over."
Police are treating injured people and carrying them away at the end Thrale Street. Members of the public were told by police to "run as fast as they could" westbound.
Nick Archer, who was in the London Bridge area, told Sky News: "We came out (of a bar) on to the road and looked and looked to my left and there as a guy, I thought he was just drinking but he was lying on the floor.
"And then a couple of seconds later, about three police vans flew past.
"He looked in a bad way."