Police attend the scene after an incident in Streatham, London, on Sunday. AP

The Metropolitan Police have said it is believed that a number of people have been stabbed in broad daylight on Streatham High Road and the incident has been declared as “terrorist-related.”

"A man has been shot by armed officers in Streatham (south London). At this stage it is believed a number of people have been stabbed. The circumstances are being assessed; the incident has been declared as terrorist-related," the police said on Twitter.

Police said later the man they had shot had been pronounced dead.

Prime Minister Boris Johnson has thanked emergency services who responded to the incident and said his thoughts “are with the injured and all those affected.”

Johnson said on Twitter: "Thank you to all emergency services responding to the incident in Streatham, which the police have now declared as terrorism-related."

"My thoughts are with the injured and all those affected," he added.

Sky News cited security sources as saying the incident was related to militancy.

Armed police cordoned off the area, on the main shopping street in Streatham, a busy residential district south of the River Thames. Police said people should avoid the area.

Several videos of the scene were posted on Twitter, but not verified by Reuters.

In one, filmed from inside a shop across the road, a man can be seen lying on the street while at least two armed police officers point their guns from behind an unmarked car with its blue lights flashing.

Helicopters flew overhead and police cars were in surrounding streets, with the area blocked off by tape.

Agencies