Two members of the public have died in a stabbing attack at London Bridge, in which police shot dead the suspect.
A further three were injured in the attack – declared a terrorist incident – and are being treated in hospital.
The suspect, who died at the scene, was wearing what is believed to have been a hoax explosive device, police said.
Videos on social media appear to show passers-by holding down a man. An officer arrives, seems to indicate to the group to move, and fires a shot.
Met Police Commissioner Cressida Dick said the attack began at Fishmonger’s Hall on London Bridge, with police called to the incident just before 14:00.
BBC journalist John McManus, who was at the scene as it unfolded, said he had seen a struggle on the bridge, with several men restraining one man. Police then arrived quickly and a number of shots were fired at him, he said.
In footage shared on social media, the man could be seen being pinned down by members of the public. Another man in a suit could be seen running from him, having apparently retrieved a large knife.
Mr Basu told a press conference: “A male suspect was shot by specialist armed officers from City of London police and I can confirm that this suspect died at the scene.”
He added that a “wide cordon remains in place” following the incident.
Mr Basu said: “Officers continue to carry out extensive searches in the area to ensure there is no further threat to the public.”