LONDON — A vehicle mowed down pedestrians on London’s Westminster Bridge, ******* at least one woman and leaving others with ******** described as catastrophic.

Around the same time Wednesday, a knife-wielding ******** stabbed a ****** officer and was shot on the grounds outside *******’s Parliament, sending the compound into lockdown.

Authorities said they were treating the ******* as a ********* ********.

The ****** level for international ********* in the U.K. was already listed at severe.

Wednesday was the anniversary of ******* ******** in the Brussels airport and subway that ****** 32 people, and the latest events echoed recent vehicle ******* in Berlin and Nice, France.

There was no immediate claim of responsibility and it was not clear if there was more than one ********. London ****** Commander B.J. Harrington said a full counter-********* ************* was underway.

The ******** in London unfolded within sight of some of the city’s most famous tourist sites, including the London Eye, a large Ferris wheel with pods that have views over the capital. It stopped rotating and footage showed the pods full as viewers watched ****** and medical crews on the bridge, which has at its north end Big Ben and Parliament, two iconic symbols.

“The whole length of the bridge there were people on the ground,” Richard Tice, a witness, told Sky News. The London Ambulance Service said it had treated at least 10 people on the bridge.

Colleen Anderson of St. Thomas’ Hospital said a female pedestrian **** and around a dozen people were hurt.

“There were some with minor ********, some catastrophic. Some had ******** they could walk away from or who have life-changing ********,” she said.

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 ***** streaming from a woman surrounded by a scattering of postcards.

“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.”

At Parliament, a body was seen lying in the yard. It wasn’t clear if it was the ********.

Dennis Burns, who was just entering Parliament for a meeting, told the Press Association he heard a radio message saying an officer had been stabbed. ****** and security rushed outside as he was going in.

“When I got inside I was wondering what the hell was going on and I saw dozens of panicked people running down the street,” he said. “The first stream was around 30 people and the second stream was 70 people. It looked like they were running for their lives.”

Daily Mail journalist Quentin Letts said he saw a man in black ****** a ****** 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.”

Lett said the other officer ran to get help and the man in black ran toward the entrance.

“As this ******** was running towards the entrance two plain-clothed guys with **** shouted at him what sounded like a warning, he ignored it and they shot two or three times and he fell,” he said.

As lawmakers were voting inside Parliament, they reported hearing the sound of ********.

Journalists there said they were told to stay in their offices. Press Association news agency reported that two people were seen lying within the grounds of Parliament.

Prime Minister Theresa May was at Parliament when the ******** began, but her office says she is safe.

British security has thwarted some 13 ****** plots over the past four years, but the UK has largely been spared major international ****** ******* such as the ones seen in Belgium and France.

Last year, a far-right supporter shot and ****** British lawmaker Jo Cox, who had campaigned for the U.K. to remain in the European Union. Prior to that, an ******** stabbed three people at a train station in east London in response to the Royal Air Force’s ******* of the Islamic State group in Syria.

The most gruesome recent ****** occurred in 2013 when two ****** converts of Nigerian descent attacked Lee Rigby, a British Army soldier who was walking down the street. The men ran Rigby down with their vehicle and then used a cleaver to hack him to ***** as bystanders watched in horror.

The ***** peace time ****** on ******* this century was on July 7, 2005, when four Al-Qaida-inspired bombers blew themselves up on three subway trains and a bus in London, ******* 52. Three of the bombers were British-born, all of Pakistani descent; the other emigrated from Jamaica.