An armed police officer stands on Parliament Square outside of the Houses of Parliament after the House of Commons sitting was suspended.

Image source, AP

BBC Political Laura Kuenssberg reports from Westminster.

House of Commons
Parliament

Commons leader David Lidington has just made a second statement, dispensing with today's business in the Commons, although MPs remain on lockdown in the chamber. 

Image source, House of COmmons

MPs are currently in lockdown in the House of Commons.

David Lidington, the leader of the House of Commons, told MPs:

"Colleagues will have appreciated that events have been moving rapidly and I want to emphasise that the knowledge that I have which is definite is so far very limited.

"What I am able to say to the House is that there has been a serious incident within the estate. It seems that a police officer has been stabbed; that the alleged assailant was shot by armed police.

"An air ambulance is attending the scene to remove the casualties. There are also reports of further violent incidents in the vicinity."

Daily Mail journalist Quentin Letts says he saw a "thick clad man dressed in black" shot by the police just below Big Ben.

Speaking to the BBC News Channel he said: "We heard what sounded like a car crash. I looked out and saw lots of members of public running down the pavement screaming and shouting.

"A thick set man in black clothes came through the gates where people drive cars into New Palace Yard.

"This man had something in his hand, it looked like a stick.

"He was challenged by two police in yellow jackets. One of these policemen fell down and we could see the man in black moving his arm in a way that was either stabbing or striking the yellow jacketed police man.

"One policeman ran to get help, which was very, very quick to come.

"As this attacker ran towards the entrance used by MPs, two plain clothes guys with guns shouted at him - uttered what sounded like a warning - and shot two or three times, and he fell.”

Prime Minister Theresa May is safe after an assailant was shot outside Parliament by armed police, a spokesman for her office said.

The spokesman declined to say where Mrs May was when the attack took place.

Telegraph chief political correspondent Christopher Hope told BBC Radio 5 live he heard a loud "bang" on Westminster Bridge before hearing "screaming, shouting" and witnessing "about 100 people running" towards Westminster Abbey.

He said this was followed by several shots, and saw two individuals "lying in the road" outside Westminster Hall. They were being treated by medics. 

Transport for London say Westminster Tube station has been closed at the request of the police. Buses are being diverted.

Image source, PA

Press Association reporter Laura Harding, who was in Westminster at the time of the incident, said: "Everyone has been evacuated into Central Lobby, including a group of schoolchildren and kitchen staff. 

"Around 15 schoolchildren aged around 10, with armed police coming through the lobby now. 

"The children are really calm, the teachers are comforting them.

"Everyone is standing around on their phones.

"There are also a bunch of young people from the Hammersmith Boxing Club in their tracksuits and the British Lionhearts boxing group."

• Witnesses say they've heard shots fired at Westminster
• Pictures have emerged of a car crashing into the railings of Parliament at the end of Westminster Bridge 
• The Leader of the House of Commons has said parliament is in lockdown 
• An ambulance has attended New Palace Yard

Read the full story here.

Commons Leader David Lidington has told MPs a "police officer has been stabbed" and the "alleged assailant was shot by armed police" following a "serious" incident within the parliamentary estate.

Former BBC employer Don Brind has told the News Channel that he saw what appears to an injured police officer and "someone clad in dark clothing lying on the ground" in the Houses of Parliament.

While walking between the main house of commons chamber and MPs offices in Portcullis House he said he was "aware of some rushing around of people then I heard a shot".

"When I looked, very close to the gates there weas a person clad in dark clothing lying on the ground with someone pointing what I assume to be a gun at him.

"A little way away was a policeman on the ground but he appeared to be conscious and talking to somebody and very quickly we were all shooed in."