A police forensic officer works near the scene after a stabbing incident in Streatham, London on Sunday, Feb. 2, 2020. London police officers shot and killed a suspect after three people were stabbed Sunday in what authorities are investigating as a terror attack. (AP)

LONDON: A man wearing what witnesses said looked like a suicide vest stabbed three people on the street in a “terrorist-related'' attack in a London neighbourhood Sunday before he was shot and killed by police, authorities said.

One victim was hospitalized with life-threatening wounds, while the others suffered less-serious injuries in the attack, which took place about 2 p.m. in the Streatham section, a combined residential and commercial neighbourhoood about  8 km south of central London, police said.

Karker Tahir said he was at work when he saw police chasing a man down Streatham High Road, the area's main shopping district.

"They kept telling him, ‘Stop! Stop!'' Tahir said. “But he didn't stop, and then I saw that they shot him three times. It was horrible seeing it. The man was on the floor and it looked like he had something, which police said may be a device. Police came to us and said, ‘You have to leave the shop because he has a bomb in his bag.'"

Images shared on social media showed a man's body on the sidewalk outside a pharmacy. Emergency medical vehicles quickly filled the street and helicopters hovered overhead.

“The circumstances are being assessed,'' the Metropolitan Police tweeted. "The incident has been declared as terrorist-related.''

The drama far from central London marked a departure from recent terror attacks in the British capital that took place near high-profile landmarks such as London Bridge and Houses of Parliament.

Investigators gave no immediate details on the attacker. But police declared the violence terrorism-related more quickly than they have in similar cases in the past, suggesting they may have had information about him.

Bell Reberio-Addy, a member of Parliament who represents Streatham, said police assured her it was an "isolated incident."

Stephen Roberts, a former deputy commissioner for the Metropolitan Police, said authorities would quickly try to search the suspect's home and seize any computer devices to scour his internet records. Investigators will be researching the man's background to learn more about the attack and any possible conspirators, he said.

Roberts said if the facts show the stabbings were carried out by a “self-starter'' _ someone acting alone _ it means that any city in the country is vulnerable to a similar sort of low-tech attack.

David Lowe, a former counterterrorism police officer, said reports suggesting the attacker may have been wearing a fake suicide vest indicate he may have wanted to die at the hands of police during the assault.