Four people, including a London police officer who was stabbed and the alleged assailant, were killed after a terror attack that saw more than 20 people injured outside the Parliament building on Wednesday.
Acting Deputy Commisssioner and Head of Counter Terrorism Mark Rowley told reporters they believe there was only one attacker. Among the injured were three police officers.
Metropolitan Police ✔@metpoliceuk
Live update re incident in #Westminster periscope.tv/w/a6FhWDEyNzM5…
"Sadly, I can confirm that now four people have died. That includes the police officer who was protecting Parliament, and one man that we believe to be the attacker who was shot by police fire at the scene," he said.
He added: "We are satisfied at this stage that it looks like there was only one attacker. But it would be foolish to be overconfident early on."
A full counter-terrorism investigation is underway.
Police said a vehicle mowed down pedestrians on London's Westminster Bridge, leaving more than a dozen with injuries described as catastrophic.
Rowley said the car then crashed near to Parliament, and at least one man - armed with a knife - continued the attack and tried to enter Parliament.
The knife-weilding attacker stabbed a police officer and was shot on the grounds outside Britain's Parliament, sending the compound into lockdown.
The threat level for international terrorism in the U.K. was already listed at severe. Wednesday was the anniversary of suicide bombings in the Brussels airport and subway that killed 32 people, and the latest events echoed recent vehicle attacks in Berlin and Nice, France.
London police were called to the Parliament building at around 2:40 p.m. local time (10:40 a.m. EST) after reports of a vehicle crashing into a crowd at Westminster Bridge near Britain's parliament.
The French prime minister said French high school students were among the injured on Wednesday.
Colleen Anderson of St Thomas' Hospital said a woman died after a vehicle apparently hit pedestrians on Westminster Bridge, near Parliament, according to the Press Association. Details on the second death are unavailable.
Anderson said: "There were people across the bridge. There were some with minor injuries, some catastrophic. Some had injuries they could walk away from or who have life-changing injuries."
A woman was also pulled alive from River Thames.
The Port of London Authority says a female member of the public was recovered from the river, injured but alive.
This is the moment Parliament was suspended as "sounds similar to gunfire" were heard outside
Rick Longley told the Press Association that he heard a bang and saw a car plow into pedestrians and come to a crashing stop. Images from the scene showed pedestrians sprawled on the ground, with blood streaming from a woman surrounded by a scattering of postcards.
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Recent Vehicular Terror Attacks:
•Jerusalem, Israel: 1/8/17
•Berlin, Germany: 12/19/16
•Ohio State: 11/28/16
•Nice, France: 7/14/16 twitter.com/metpoliceuk/st…
"They were just laying there and then the whole crowd just surged around the corner by the gates just opposite Big Ben," he said. "A guy came past my right shoulder with a big knife and just started plunging it into the policeman. I have never seen anything like that. I just can't believe what I just saw."
The former Polish foreign minister Radoslaw Sikorski posted a video on Twitter that seems to show people lying injured in the road on Westminster Bridge.
Sikorski, a senior fellow at the Harvard Centre for European Studies, says he saw at least five people lying on the ground after being "mown down" by a car.
Sikorski told the BBC he "heard what I thought what I thought was just a collision and then I looked through the window of the taxi and someone down, obviously in great distress.
"Then I saw a second person down, and I started filming, then I saw three more people down, one of them bleeding profusely."
Prime Minister Theresa May was rushed to safety after the attack.
May will chair a meeting of the government emergency committee to discuss the response to the terror incident in London.
The emergency committee known as Cobra coordinates the high-level response to serious incidents. It brings together government ministers with senior officials of the emergency services and security and intelligence agencies.
The White House is condemning the attacks and President Trump President Donald Trump is said to be monitoring developments.
George Freeman MP ✔@Freeman_George
Incredibly brave @metpoliceuk anti-terror officers co-ordinating a lockdown & evacuation after #ParliamentAttack
Spokesman Sean Spicer said Wednesday Trump spoke with British Prime Minister Theresa May and said that the White House applauds "the quick response of British police and first responders" and condemns the attacks.The U.S. State Department says it is closely monitoring the incident and urged Americans in London to avoid the area.
Spokesman Mark Toner said Wednesday: "We stand ready to assist in any way the U.K. authorities would find helpful."
He added that the U.S. Embassy in London is closely following the news and stands ready to help any affected Americans.
He said: "Our hearts go out to those affected."
Daily Mail journalist Quentin Letts said he saw a man in black attack a police officer outside Parliament before being shot two or three times as he tried to storm into the House of Commons.
"He had something in his hand, it looked like a stick of some sort, and he was challenged by a couple of policemen in yellow jackets," Letts told the BBC. "And one of the yellow-jacketed policemen fell down and we could see the man in black moving his arm in a way that suggested he was stabbing or striking the yellow-jacketed policeman."
Witness Jayne Wilkinson told the Telegraph: "We were taking photos of Big Ben and we saw all the people running towards us, and then there was an Asian guy in about his 40s carrying a knife about seven or eight inches long."
British security has thwarted some 13 terror plots over the past four years, but the UK has largely been spared major international terror attacks such as the ones seen in Belgium and France.
The incident Wednesday comes on the one-year anniversary of the terror attacks in Brussels in which 32 people were killed and more than 300 injured. ISIS claimed responsibility for the coordinated suicide bombings -- two at the Brussels Airport in Zaventem and one at Maalbeek metro station in central Brussels. The bombings were the deadliest terror attack in Belgium's history.
ISIS has long promoted the use of vehicles and knives in attacks by so-called "lone wolf" terrorists, particularly in Western countries. The terrorist group has not claimed responsibility for Wednesday's attack.
