LONDON - British police are responding to incidents across London following reports of a vehicle slamming into pedestrians on the London Bridge.

Police say there is more than one fatality following the three separate incidents, the BBC reports. 

A witness who was on the bridge told the BBC she saw a speeding van veer onto the pavement, striking as many as six people. Police then responded to reports of incidents at two more sites. Live updates are below:

The Metropolitan Police said on Twitter they responded to reports of a collision on the bridge shortly after 11 p.m. local time, followed by reports of a stabbing at Borough Market. Armed police responded and shots were fired, police said. Police further said armed officers were responding to a third incident in the Vauxhall area. 

The BBC reports police are searching for three suspects who could be armed, according to Reuters.

British Prime Minister Theresa May has been briefed on the incident and is in touch with officials, Downing Street said. White House press secretary Sean Spicer said President Trump has also been briefed on the situation.

President Trump responded to the incident with a message of support on Twitter. "Whatever the United States can do to help out in London and the U.K., we will be there," he tweeted. "WE ARE WITH YOU. GOD BLESS!"

The city transit authority Transport for London closed the bridge and ordered the London Bridge underground station evacuated.

One witness inside the station described the scene to Sky News. 

"I was walking out of the London Bridge station and there were police," Caroline Breniere said. "Some of them were coming by car, some of them were running. The traffic was stopped."

Another man who was nearby told Sky he witnessed emergency vehicles rushing to the scene.

"We finished drinking at a bar and we came out onto the road and I looked to my left and there was a guy, we thought he was just drunk, he was lying on the floor," the man told Sky. "A couple seconds later, about three police vans flew past. The guys who were with the guy that was on the floor managed to flag one of the police vans down. One of the officers jumped out and started attending to the guy on the floor."

Will Haven, managing editor of The Spectator in London, told Sky he "certainly saw people who looked like they'd been run over."

On March 22, a knife-wielding man mowed down pedestrians on London's Westminster Bridge before fatally stabbing an armed police officer to death just inside the gates of Parliament. Five people were killed, including the attacker, and at least 40 people were injured.

A State Department spokesperson said U.S. officials are closely monitoring the incidents in London.

"Our thoughts are with the family and friends of those affected by this terrible situation," the spokesperson said in a statement to CBS News. "We stand ready to provide all possible consular assistance should we become aware of any affected U.S. citizens."