The Metropolitan Police have confirmed a stabbing incident at London Bridge was a terrorist attack, and that the male suspect was shot dead at the scene.
In a statement, Neil Basu, the head of UK counter-terrorism policing, said the knifeman had been wearing a hoax explosive device.
He was shot by armed specialist officers and died at the scene.
Police were called at 1:58pm to reports of a stabbing at a premises near to the central London landmark.
The London Ambulance Service declared it a "major incident" after a number of people were injured. The number of casualities has not yet been confirmed.
A bystander took hold of the knife used by the attacker
Armed police remain at the scene and police dogs have been deployed.
A large area around London Bridge has been cordoned off by police, and the area surrounding Borough Market has been evacuated.
London Bridge station has also been closed.
Mr Basu said cordens would be in place for a "considerable time" as police ensure there are no further threats to the public.
An eyewitness told talkRADIO: "We were just in our van and everybody started running."
The incident occured at around 13:58 this afternoon
The Prime Minister thanked the emergency services, saying: "I'm being kept updated on the incident at London Bridge and want to thank the police and all emergency services for their immediate response."
And London Mayor Sadiq Khan said in a statement: "The Metropolitan Police have confirmed that as a precaution the horrendous incident at London Bridge is being treated as though it is terrorism-related.
"I remain in close contact with the Metropolitan Police and am being kept updated with events. It has been confirmed that people were injured in the attack. My heart goes out to them, their families and all affected.
"Thank you to our brave emergency services who responded to tooday’s horrific attack. Every day they put their lives on the line for us – running towards danger to keep London safe."
talkRADIO: Listen live