Westminster attack: Woman killed, others left with 'catastrophic' injuries

London Ambulance said they treated at least 10 people who sustained injuries on the bridge.

Colleen Anderson of St Thomas' Hospital said one female pedestrian has died.

"There were people across the bridge. There were some with minor injuries, some catastrophic. Some had injuries they could walk away from or who have life-changing injuries," Anderson said.

A London police commander said police officers were among the injured.

Eyewitnesses told British media the attacker mowed down pedestrians on Westminster Bridge before crashing his car into railings outside the Houses of Parliament then running out with a knife, stabbing a police officer and then being shot.

Daily Mail journalist Quentin Letts said: "This man had something in his hand, it looked like a stick of some sort and he was challenged by a couple of policemen in yellow jackets and one of the yellow jacketed policemen fell down.

"And we could see the man in black moving his arm in a way that suggested he was either stabbing or striking the yellow jacketed policeman and one of the policemen then ran to get help which was very quick to come.

"And as this attacker was running towards the entrance used by MPs to into the House of Commons, as he was running he ran about I'd say 15 yards - perhaps two plain clothes guys with guns shouted at him what sounded like a warning, he ignored it and they shot two or three times and he fell."

The UK parliament went into lock-down following the attack, that targetted one of London's busiest bridges.

London's Scotland Yard said an investigation is ongoing, but at this stage the nature of the attack cannot be confirmed.

The police warned the public to stay away from the area as they deal with the incident.

An emergency security meeting, headed by Prime Minister Theresa May, has been scheduled for Wednesday evening.