LONDON (AP, REUTERS, BLOOMBERG) - British police shot a man on London Bridge in the heart of Britain's capital on Friday (Nov 29) after a stabbing that left several people wounded.

UK's top counter-terrorism official Neil Basu said at a press conference that the incident has been "declared a terrorist incident," adding that the suspect, who was wearing a 'hoax' explosive device, had been shot dead.

Scores of police, some armed with submachine guns, rushed to the scene after reports of a stabbing, ushering bemused office workers and tourists out of an area packed with office buildings, banks, restaurants and bars. Staff in office blocks in the area were told to stay inside.

The police force said officers were called just before 2pm local time (10pm Singapore time) "to a stabbing at premises near to London Bridge," which links the city's business district with the south bank of the River Thames.

They said a man was detained and "a number of people have been injured."

Armed officers burst into restaurants in the Borough Market area at London Bridge and urged diners to leave as fast as possible.

They shouted "Out, out, out," to people at the Black and Blue bar. Diners walked away with their hands on their heads.

Nearby, police shouted to pedestrians to "run." Officers closed off the bridge and evacuated passers-by from the surrounding area.

On the north bank of the River Thames, police officers shouted to pedestrians to move back from the bridge 100 metres, and then urged them to take shelter in any nearby building, shouting: "Move inside for your own safety."

Witnesses meanwhile reported seeing what appeared to be fighting on the bridge and hearing several gunshots.

One video posted on social media showed two men struggling on the bridge before police pulled a man in civilian clothes off a black-clad man on the ground. Shots then rang out.

Other images showed police, guns drawn, pointing at a figure on the ground in the distance.

Ms Amanda Hunter said she was on a bus crossing the bridge when she heard shots. "(The bus) all of a sudden stopped and there was commotion and I looked out the window and I just saw these three police officers going over to a man," she told the BBC.

"It seemed like there was something in his hand, I'm not 100% sure, but then one of the police officers shot him."

Ms Karen Bosch, who was also on a bus, said she saw police "wrestling with one tall, bearded man" and then heard "gunshots, two loud pops."

She said the man "pulled his coat back which showed that he had some sort of vest underneath, whether it's a stab vest, or some sort of explosive vest, the police then really quickly moved backwards, away."

Cars and buses on the busy bridge were at a standstill after the shooting, with a white truck stopped diagonally across the lanes. Video footage showed police pointing guns at the truck before moving to check its container.

British Transport Police said London Bridge station, one of the city's busiest rail hubs, was closed and trains were not stopping there.

City of London Police, the force responsible for the business district, urged people to stay away from the area.

The incident revived memories of the June 2017 London Bridge attack, when three Islamic State-inspired attackers ran down people on the bridge, killing two, before stabbing several people to death in nearby Borough Market.

That incident took place days before a general election. Britons are due to go to the polls again on Dec 12.

"This is an appalling incident and all my thoughts are with the victims and their families," British Prime Minister Boris Johnson said.

In March 2017, an attacker fatally struck four people with a car on nearby Westminster Bridge then fatally stabbed a police officer before security forces shot and killed him in a courtyard outside Parliament.