An eyewitness has spoken about the moment an alleged Westminster attacker ran past him and stabbed a police officer.

Asked to describe what he saw, the witness recounted how he was walking to the station when he heard a loud bang.

He recalls seeing a car mount the pavement, ploughing down pedestrians in its path.

In pictures: Westminster attack Show all 9 1 /9 In pictures: Westminster attack In pictures: Westminster attack An air ambulance lands after gunfire sounds were heard close to the Palace of Westminster in London PA wire In pictures: Westminster attack MPs wait until the situation is under control in Westminster. 'The alleged assailant was shot by armed police,' David Lidington, leader of the House of Commons, told the house. BBC News In pictures: Westminster attack Crowds gather in Westminster after shooting incident, which police are treating as terror attack BBC News In pictures: Westminster attack Police were also called to an incident on Westminster Bridge nearby AP In pictures: Westminster attack Early reports indicate the car, which mounted the pavement on Westminster Bridge and mowed into around a dozen people, was the same vehicle which then rammed into the railings of the Palace of Westminster, just around the corner Reuters In pictures: Westminster attack Security sources described the suspected assailant as a middle-aged Asian man, who is understood to have left the car before attacking a police officer with a seven-to-eight inch knife PA wire In pictures: Westminster attack Police have asked people to avoid the immediate area to allow emergency services to deal with the ongoing incident AP In pictures: Westminster attack One woman has died and a number of others, including the police officer, have been hurt, according to a junior doctor at St Thomas' Hospital Reuters In pictures: Westminster attack At least three gun shots were heard by those inside Westminster, and proceedings in the House of Commons have been suspended AP

According to the man, the crowd immediately ‘surged’ around the corner by the gates opposite the Big Ben.

“A guy came past my right shoulder with a big knife, and just started plunging it into the policeman,” he said.

The alleged assailant was shot by armed police.

The Metropolitan Police are treating it as a terror incident.

They released a statement saying: “We are treating this as a terrorist incident until we know otherwise.

”Officers - including firearms officers - remain on the scene."

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