The attacker mowed down several pedestrians as he drove a grey Hyundai i40 across Westminster Bridge before crashing it into railings then running through the gates of the Palace of Westminster and stabbing the officer.

At least 20 people were injured when the car mowed them down on a central London bridge.

The knifeman was shot by police in the shadow of Big Ben, as he had tried to force his way into a courtyard just outside the Houses of Parliament.

Conservative parliamentarian Tobias Ellwood, whose brother was killed in the Bali terror attack in 2002, performed mouth-to-mouth resuscitation on the police officer who was stabbed and later died. About 10 metres away from the police officer was the attacker who was shot dead by police after scaling the security wall toward the Parliament's grounds.

Ellwood, who served in the British military and served in Bosnia, Northern Ireland, Kuwait and Cyprus, applied pressure to the police officer's multiple lacerations.

Photographs showed Ellwood's bloodied hands and face from the police officer's wounds while the alleged attacker was seen nearby.



It is believed there is only one assailant, but a thorough search of the area is underway.

London mayor, Sadiq Khan, says he's grateful the police and emergency services could show "tremendous bravery in exceptionally difficult circumstances," and additional officers will be on patrol tonight to ensure the safety of Londoners.