LONDON (KRON) — Five people are were killed including a police officer and the attacker in what authorities are treating as a terrorist incident.

Counter-terrorism chief Mark Rowley said one policeman, three civilians, and the attacker died.

Rowley said a further 40 people were wounded. He identified the police officer who died as Keith Palmer, 48.

The assailant has not been identified. Rowley said police think they know the identity of the man but would not reveal details. He said Islamic extremism is suspected in the attack.

Witnesses said a vehicle struck several people on the Westminster Bridge and photos showed a car plowed into railings. Around the same time Wednesday, a knife-wielding attacker stabbed a police officer and was shot on the grounds outside Britain’s Parliament, sending the compound into lockdown.

At least one woman has been killed, others have ‘catastrophic’ injuries in Westminster Bridge incident, UK Press Association reports.

London’s Metropolitan Police said on Twitter they were called at approximately 2:40 pm to reports of a firearms incident near Westminster Bridge.

Police also said in a statement they were “treating this as a terrorist incident until we know otherwise.”

London police say they believe there was only 1 attacker.(Video of car courtesy of @claudiascore)

The incident occurred as parliament was in session, and proceedings in the House of Commons were suspended.

Dozens of MPs remain in the House.

TV images have emerged of a car crashed into perimeter fence outside the Parliament building.

“It seems that a police officer has been stabbed, that the alleged assailant was shot by armed police,” House leader David Lidington told MPs.

He confirmed that a serious incident had taken place “within the estate.”

“An air ambulance is currently attending the scene to remove the casualties. There are also reports of further violent incidents in the vicinity of the Palace of Westminster but I hope colleagues on all sides will appreciate that it’d be wrong of me to go into further details here until we have confirmation from the police and from the House security authorities about what is going on.”

Henry Mance, a political reporter for the Financial Times, told CNN that people inside have been told to stay away from windows.

Armed officers have been sent inside parliament.

Member of parliament Sir Gerald Howarth said the House was in the middle of a vote when the session was suspended and members locked in.

“It appears to be very, very serious indeed. The Leader of the House has told us it’s been confirmed that one police officer here has been stabbed. It appeared that a car was coming towards the House of Commons mowing down pedestrians on the way and the driver then got access to the parliamentary estate stabbed a police officer and was shot,” he said.

Extra armed police would be on the streets in the coming days to reassure the public, and hundreds of police officers are working on the case.

The White House says U.S. 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 U.S. will continue to monitor the situation and update the president.