A police officer has been stabbed and a suspected assailant shot outside the Houses of Parliament, shortly after a car is reported to have rammed into members of the public on Westminster Bridge.
At least three gun shots were heard by those inside Westminster, and proceedings in the House of Commons have been suspended as police deal with the "serious" security incident.
The deputy speaker of the Commons, David Lidington, announced the suspension in the House, saying a police officer had been stabbed and the "alleged assailant shot by armed police".
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 gates of Westminster just around the corner.
Witnesses described at least one middle-aged man leaving the car and attacking a police officer with a seven-to-eight inch knife, before being shot.
The police officer was seen wounded but moving, after falling to the ground clutching his arm or shoulder. At least one man was seen running towards the exit of New Palace Yard, underneath Big Ben.
Police were seen shouting at him, presumably to stop. Shots were then heard. It is unclear at this stage whether one or more men were involved.
"We are aware of reports of an incident at Westminster. We will put more information out as soon as we can," Metropolitan Police tweeted.
"We were called at approx 2.40pm to reports of an incident at Westminster Bridge. Being treated as a firearms incident - police on scene."
A Downing Street source confirmed that Prime Minister Theresa May, who was inside the Commons at the time, was "OK".
Ms May was seen being ushered into a silver Jaguar car as what sounded like gunfire rang out during the incident at around 2.45pm.
A witness said she saw around 100 panicked members of the public running from the scene.
She told the Press Association: "As I was coming through the doors at Portcullis House, a policeman grabbed someone who was coming in and threw him out.
"As we were coming though the glass doors I was told by one security guard to get out while another one told me to get in.
"As I walked in I heard a security guard get a radio message saying 'a policeman has been stabbed'.
"Then I walked in as police officers and security start rushing out of the front doors on to the street.
"When I got inside I was wondering what the hell was going on and I saw dozens of panicked people running down the street. The first stream was around 30 people and the second stream was 70 people.
"It looked like they were running for their lives."
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