LONDON — The latest on reports of an incident outside Britain's parliament (all times local):

3:50 pm

Witness Rick Longley told the Press Association that he saw a man stab a policeman outside Britain's Parliament.

"We were just walking up to the station and there was a loud bang and a guy, someone, crashed a car and took some pedestrians out," he said.

"They were just laying there and then the whole crowd just surged around the corner by the gates just opposite Big Ben.

"A guy came past my right shoulder with a big knife and just started plunging it into the policeman.

"I have never seen anything like that. I just can't believe what I just saw."Lawmaker Adam Holloway told the AP he saw people running and immediately ran into his offices in Parliament to be with his staff. "A lot of us are locked in with our staff at the moment," he said.

3:50 pm

The White House says US President Donald Trump has been briefed on a gun and knife incident at Britain's Parliament in London.

Trump himself said during a brief appearance Wednesday before reporters at the White House that he was just getting the news. He called it "big news." Trump's spokesman, Sean Spicer, says the US will continue to monitor the situation and update the president. Britain's Parliament was on lockdown after — according to officials — an assailant stabbed an officer then was shot by police.

London Police also said officers were called to an incident on nearby Westminster Bridge

3:40 pm

British lawmaker Grant Shapps said on Twitter that he was walking through the cloisters of the House of Commons to vote when he heard four gunshots. Police told lawmakers to get down on the ground and crawl to cover.

"Police response instant. Heard commotion, looked round. Police weapons drawn, 4 shots, police ordered us to hit ground & get back, get back," he said.

3:40 pm

The former Polish foreign minister Radoslaw Sikorski posted a video on Twitter that seems to show people lying injured in the road on Westminster Bridge.

Sikorski, a senior fellow at the Harvard Centre for European Studies, says he saw at least five people lying on the ground after being "mown down" by a car.

Sikorski told the BBC he "heard what I thought was just a collision and then I looked through the window of the taxi and someone down, obviously in great distress.

"Then I saw a second person down, and I started filming, then I saw three more people down, one of them bleeding profusely."

3:35 pm

London police say they are treating a gun and knife incident at Britain's Parliament "as a terrorist incident until we know otherwise."The Metropolitan Police says in a statement that the incident is ongoing. It is urging people to stay away from the area.

Officials say a man with a knife attacked a police officer at Parliament and was shot by officers.

There are also reports of a vehicle hitting pedestrians on nearby Westminster Bridge.