Police have responded to a new incident close to London Bridge.
Armed officers arrived at Borough Market It is not clear if the incidents are linked. \
Officers have then responded to reports of stabbings in Borough Market. Armed officers responded and shots were been fired.
Police say a vehicle and a knife may have been used in the initial incident on London Bridge.
An eyewitness said a van veered off the road and hit pedestrians as pictures show people being treated at the scene by emergency services.
Police say they are 'searching for three suspects'.
Police are also dealing with an incident in Vauxhall nearby.
The first incident was called in at 10:15.
A Downing Street spokesman said: "The Prime Minister is in contact with officials and is being regularly updated on the incident at London Bridge."
London Bridge is closed both ways Transport for London (TfL) said, warning the public to avoid the area.
Trains are currently not stopping at London Bridge or Borough stations.
Scotland Yard said officers were at the scene and it would update with further information.
London Ambulance said multiple resources were attending the area.
Holly Jones, a BBC reporter at the 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."
More to follow.