The Metropolitan Police has said it is dealing with an incident at London Bridge amid reports of shots being fired.
The force tweeted: "We are currently dealing with an incident at London Bridge. Please stand by for updates."
Various social media users have reported hearing gunshots from London Bridge.
One video shows what appears to be police pulling equipment out of a vehicle nearby.
Those in the video can be heard saying: "They've actually got guns out. They've got the guns out."
BBC correspondent John McManus told BBC News that he had heard several gun shots on London Bridge.
"Just a few minutes ago I was walking across London Bridge on the south bank to the north bank of the bridge," he said.
"There appeared to be a fight going on on the other side of the bridge, with several men attacking one man."
Political commentator Owen Jones tweeted: "I'm near London Bridge, looks like a bad incident - people running, police yelling 'keep moving', lots of emergency services, area cordoned off. Stay safe everyone."
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