British police shot a man on Friday after a stabbing in the London Bridge area, a security source told Reuters.
Videos and photographs on Twitter showed several police cars and buses on the bridge and a truck straddling several lanes.
A 14-second video clip on Twitter filmed from a high vantage point on the opposite side of the street showed what appeared to be three police officers backing away from a man lying on the pavement.
Two of the officers are pointing rifles at the man, who can be seen moving slightly. Reuters could not independently verify the footage.
“Police were called at 1:58 p.m. to a stabbing at premises near to London Bridge,” police said in a statement. “A man has been detained by police. We believe a number of people have been injured.”
Witnesses told British media that the police arrived quickly at the scene soon after shots were heard.
It is believed somebody was stabbed in the London Bridge and police have shot a suspect, a security source told Reuters.
London’s ambulance service said it had declared it a major incident and they had sent several crews to the scene.
A police spokesman said earlier: “It appears somebody has been shot.”
Sky News said a man had been shot dead.
London Bridge was the scene of an attack in June 2017 when three militants drove a van into pedestrians and then attacked people in the surrounding area, killing eight people.
Earlier this month, Britain lowered its national terrorism threat level to “substantial” from “severe”, its lowest level since 2014.
London Bridge station was closed.