Two members of the public have died and three more are injured after a knifeman wearing a hoax suicide vest launched a terror attack on London Bridge.
"At this early stage, the circumstances relating to the incident remain unclear", notes an official statement released by Metropolitan Police.
The members of the public then disperse and the man appears to be shot by police as he lay on the ground.
Prime Minister Boris Johnson was on his way back to Downing Street and Basu said he would be giving him a full briefing.
Pictures show a white lorry blocking both carriageways of the road across the bridge.
Police said they were treating the evacuation of the area surrounding Borough Market as a "major incident'".
He said their "appeared to be a fight going on" with one man being attacked by others.
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As a result of the attack, several people were injured and the suspected perpetrator detained, the police said.
The following is a Reuters summary of what we know and do not know about the incident.
It said: "A man has been detained by police". Sky News reported that the police had shot the apparent attacker.
The City of London police, the force responsible for the business district, urged people to stay away from the area.
The bridge had to be cordoned off.
She said the manager ran to lock the doors and staff told people to move away from the front of the restaurant. My heart goes out to them, their families and all affected. "Gunshots", said the woman.
The U.K.is set to hold a general election on December 12 and the last election campaign in 2017 was interrupted by attacks, including one that killed eight people in the same area of London.
One video shows what appears to be police pulling equipment out of a vehicle nearby.