A major security alert has been raised at the Palace of Westminster this afternoon.
Here’s everything we know so far as the situation develops.
What happened?
It is understood a car drove along Westminster Bridge, crashing into the gates of Parliament before an assailant jumped out and stabbed a police officer. He was then shot. Witnesses have reported hearing loud bangs similar to gun fire as the incident unfolded.
There were scenes of panic and chaos as pedestrians ran away from the scene and emergency services descended on the area.
Have there been any casualties?
Four people were killed in the Westminster terror attack, including the police officer who was stabbed and his attacker, Scotland Yard’s top anti-terror officer Mark Rowley has confirmed.
A number of others have been hurt – including some with “catastrophic” injuries – in the incident on Westminster Bridge, a junior doctor at St Thomas’ Hospital has said.
The police officer who was stabbed by the knifeman has also died.
Witnesses also reported around eight to 10 people were lying on Westminster Bridge after being struck by the car. The severity of their injuries are still unknown.
Three French teenagers were among those injured on Westminster Bridge.
Le Telegramme reported the students, aged between 15 and 16, were wounded in the attack with one ending up on the roof of the car.
The pupils from a school in Concarneau, Brittany, had arrived in London on Sunday evening.
A spokeswoman for the Lycee Saint-Joseph de Concarneau confirmed three students were injured but said she could give no further information.
Meanwhile, French President Francois Hollande said: “Terrorism concerns us all and France knows how the British people are suffering today.
“We are doing everything to find out if French nationals have been involved.”
What happened next?
The sitting in the House of Commons was suspended while police officers sealed off the area around the incident. Staff, journalists and politicians inside Parliament were told to stay inside.
Westminster underground station has been shut at the police’s request.
The Met Police are apparently treating the incident as terrorism.
A counter-terrorism investigation is already under way, police said.
Giving a statement outside Scotland Yard, police spokesman Commander BJ Harrington said: “A senior national coordinator has declared this a terrorist incident.
“Although we remain open-minded to the motive, a counter-terrorism investigation is already under way led by the Met counter-terrorism command.
“We received a number of different reports which included a body in the river, a car in collision with pedestrians and a man armed with a knife.
“Officers were already in the location as part of routine policing but immediately additional officers were sent.”
The force is also appealing for anyone with photos or footage of the incidents to pass it to them.
“If you have photos or film of the incident in Westminster please make sure you pass them to police
http://www.ukpoliceimageappeal.co.uk
” the force tweeted.
Prime Minster Theresa May’s official spokesman said: “The Prime Minister was brought back to Number 10 from Parliament. She is currently monitoring the situation.”
The office of the Serjeant at Arms, who handles security in the House of Commons, said: “We are aware that there has been an incident that has taken place.
“At this early stage, we cannot comment further.”
Mayor of London Sadiq Khan said: “There has been a serious incident near to Parliament Square this afternoon which is being treated as a terrorist attack until the police know otherwise.
“I have spoken to the Acting Commissioner. The Metropolitan Police Service is dealing with the incident and an urgent investigation is under way. My thoughts are with those affected and their families.
“I would like to express my thanks to the police and emergency services who work so hard to keep us safe and show tremendous bravery in exceptionally difficult circumstances.
“For the latest information please visit news.met.police.uk.”
Buckingham Palace declined to comment about its security arrangements in light of the terrorist incident and referred all inquiries to the Met Police.
But with the Royal Standard flying above the palace – indicating the Queen was in residence – it was clear some precautions had been taken as the gates, patrolled by armed police, had been closed.
US President Donald Trump has spoken to Mrs May about the attack, his spokesman Sean Spicer said, adding: “We condemn’s today’s attack.”
US Secretary of State Rex Tillerson said: “On behalf of the United States, I express my condolences to the victims and their families.
“The American people send their thoughts and prayers to the people of the United Kingdom.
“We condemn these horrific acts of violence, and whether they were carried out by troubled individuals or by terrorists, the victims know no difference.”
Meanwhile the Scottish Parliament has suspended its independence referendum debate following the attack.
First Minister Nicola Sturgeon tweeted:
My thoughts are with everyone in and around Westminster caught up in this dreadful incident – and with the brave emergency services.
— Nicola Sturgeon (@NicolaSturgeon) March 22, 2017
Hundreds of people were evacuated from Parliament to Westminster Abbey.
Addressing the crowd, which included ministers, MPs, peers and tourists, from the pulpit a Met Police superintendent said it would take around 90 minutes to process everyone.
An email address and website was given out so eyewitnesses can upload any pictures or videos of what happened for use in evidence.
Police said people would be assessed to see if they have any information.
A prayer was then said for the victims of the attack.
