A police officer has died after being stabbed inside the grounds of Parliament during a major terror incident in the heart of London, police have confirmed.

The attack, which happened just after lunchtime, involved a car which is believed to have run into pedestrians on Westminster Bridge, before continuing into railings outside Parliament.

The driver is believed to have then got out of the car and stabbed the officer before being shot.

Scotland Yard's anti-terror lead, Mark Rowley, said the officer was among four people killed. One of those is the attacker. A further twenty people were injured.

Mr Rowley said the dead policeman - who was unarmed - was one of the officers tasked with guarding Parliament. His family has been informed.

Tory MP Tobias Ellwood, who treated the injured police officer at the scene, also confirmed he had died.

The foreign minister – a retired soldier - reportedly attempted to perform mouth-to-mouth on the officer.

Police earlier confirmed there were a number of casualties, including police officers.

Westminster terror attack: At least two dead

Commander BJ Harrington said: "We know there are a number of casualties including police officers but at this stage we cannot confirm numbers or the nature of these injuries.

"We received a number of different reports which included a person in the river, a car in collision with pedestrians and a man armed with a knife."