LONDON — At least three people, including a police officer, were killed, and at least 20 injured, Acting Deputy Commissioner of the Met Police Mark Rowley told reporters outside Scotland Yard.
He added the police currently believe there was only one attacker, who was killed, but are continuing to investigate.
The Leader of the House of Commons said a police officer was stabbed. Many of those hurt had “catastrophic injuries”, PA said.
“Officers — including firearms officers — remain on the scene and we are treating this as a terrorist incident until we know otherwise,” police said.
London’s Metropolitan Police said on Twitter they were called at approximately 2:40 pm to reports of a firearms incident near Westminster Bridge, near the main parliament building.
The incident occurred as parliament was in session, and proceedings in the House of Commons were suspended. Dozens of MPs remained in the House.
“It seems that a police officer has been stabbed, that the alleged assailant was shot by armed police,” the Leader of the House, David Lidington, told MPs.
He confirmed that a serious incident had taken place “within the estate.”
“An air ambulance is currently attending the scene to remove the casualties. There are also reports of further violent incidents in the vicinity of the Palace of Westminster but I hope colleagues on all sides will appreciate that it’d be wrong of me to go into further details here until we have confirmation from the police and from the House security authorities about what is going on.”
Around half an hour after the attack, former Cabinet minister Anna Soubry said on Twitter she and Security Minister Ben Wallace were ordered into the Parliament lobby at gun point by police.
“Colleagues taken out of the library at gun point by counter terrorist armed police officers,” she tweeted.
People were photographed running from the scene as police put the whole area in lockdown.
Police said in a statement that a full response unit had been sent to the scene, along with ambulance crews and air ambulances.
“We have declared a major incident and our priority is to assess patients and ensure that they are treated and taken to hospital as soon as possible.”
Police appealed for anyone with photos or video of the incident to pass them on to police.
TV images have emerged of a car crashed into perimeter fence outside the Parliament building.
US President Donald Trump at a Women in Healthcare panel told reporters he was getting updates from London.
“Some big news having to do with London just happened,” he said.
The US State Department is also closely monitoring the situation and “stands ready to assist in any way the UK authorities would find helpful,” acting spokesman Mark Toner said.
“The safety and security of US citizens overseas is one of our highest priorities,” he told CNN. “We urge US citizens in London to contact family members and loved ones to notify them that you are safe, to avoid the area and monitor local news.”
Member of parliament Sir Gerald Howarth said the House of Commons was in the middle of a vote when the session was suspended and members locked in.
“It appears to be very, very serious indeed. The Leader of the House has told us it’s been confirmed that one police officer here has been stabbed. It appeared that a car was coming towards the House of Commons mowing down pedestrians on the way and the driver then got access to the parliamentary estate stabbed a police officer and was shot,” he said.