Eyewitness video showed police cars blocking the road over London Bridge on Friday (November 29) after police said they had been called to a stabbing incident in the area.
Police said a number of people had been injured and a suspect detained. A security source told Reuters that police shot a man after the stabbing.
London’s ambulance service said it had declared it a major incident and they had sent several crews to the scene.
Videos and photographs on Twitter showed several police cars and buses on the bridge and a truck straddling several lanes.
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.
(Production: Kevin Donnellan, Rosalind Church)