LONDON — The British government raised its terrorism threat warning to its second-highest level on Monday, after police labeled two attacks in the past month — a car explosion outside a Liverpool hospital and the fatal stabbing of a British lawmaker — terrorist incidents.

The government announced it was upgrading its terrorism threat level from “substantial” to “severe” — meaning that the government considers the possibility of an attack “highly likely.”

The move came after an incident Sunday morning, when a taxi pulled up outside an entrance to Liverpool Women’s Hospital in northwestern England. Video footage shows a blast ripping through the vehicle, which then burst into flames. Police said that the blast killed the passenger in the car, who they suspect was carrying a homemade bomb.

Police arrested four men in relation to Sunday’s car explosion, but they were released after questioning on Monday.

CCTV captured the moment a taxi exploded outside a hospital in the northern English city of Liverpool on Nov. 14. (Reuters)

Although police declared the car explosion a “terrorist incident,” they did not release any details to support that conclusion and said the motive was unclear.

On Monday evening, police identified the deceased and indicated he was a suspect in the bombing.

“Our inquiries are very much ongoing but at this stage we strongly believe that the deceased is 32-year-old Emad al Swealmeen,” detective chief inspector Andrew Meeks said in a short statement. He said that al Swealmeen was linked to two addresses the police raided following the incident, including one address where he recently rented and where police had found “significant items.”

“We continue to appeal for any information about this incident and, now that we have released his name, any information that the public may have about al Swealmeen, no matter how small, may be of great assistance to us,” Meeks said.

Russ Jackson, head of counterterrorism policing in northwestern England, said earlier Monday that “although the motivation for this incident is yet to be understood, given all the circumstances, it has been declared a terrorist incident and counterterrorism policing are continuing with the investigation.”

Prime Minister Boris Johnson chaired a meeting of COBRA, the government’s crisis committee, Monday afternoon in response to the attack. Speaking later at a news conference at Downing Street, Johnson downplayed the security risk, saying that the national terrorism threat levels “bump around.” The elevated alert stemmed from the “number of attacks, failed or successful” within a short space of time, he said.

“What we’re really saying to the public, as a result of what happened in Liverpool, is that everybody’s got to be vigilant,” he said.

Last month, a 25-year-old man was charged under terrorism legislation in the fatal stabbing of Conservative lawmaker David Amess.

Amess, 69, was meeting with constituents in a church building in his home district in Essex, England, when he was stabbed Oct. 15.

The car explosion occurred Sunday just before 11 a.m. Jackson said that the incident involved the ignition of an explosive device and that it was the passenger who brought the homemade bomb into the cab. That passenger, believed to be al Swealmeen, was declared dead at the scene.

The taxi driver, named by the British media as David Perry, escaped the car moments after the explosion. He was hospitalized in stable condition and subsequently released.

“Our enquiries will now continue to seek to understand how the device was built, the motivation for the incident and to understand if anyone else was involved in it,” Jackson said in a statement he read out at a news briefing.

It’s unclear why the women’s hospital was targeted. Police said the passenger had been picked up about 10 minutes away and had asked to be taken to the hospital.

Questions have been raised about the timing of the blast, which occurred on Remembrance Sunday, a day when Britain pays tribute to its war dead by observing two minutes of silence at 11 a.m. Officers said that they have not drawn any link between the occasion and the incident but that it remains a “line of inquiry.”

Some have wondered whether the bomber was planning to walk over to nearby Liverpool Cathedral to detonate the device as people spilled out of a Remembrance Sunday service.

Perry, the taxi driver, was lucky to be alive, his wife said. Writing on social media, Rachel Perry said that her husband was “extremely sore and just trying to process what’s happened.”

She also seemed to downplay the suggestion that he had locked the passenger inside the cab after growing suspicious about his intentions. Earlier, the mayor of Liverpool, Joanne Anderson, told the BBC that the taxi driver had “locked the doors” of his cab, and through his “heroic efforts has managed to divert what could have been an absolutely awful disaster.” Johnson, the prime minister, said that the driver appeared to have acted with “incredible presence of mind and bravery.”

“There are a lot of rumours flying round about him being a hero and locking the passenger inside the car … but the truth of the matter is, he is without a doubt lucky to be alive,” Rachel Perry wrote on her post, according to the Manchester Evening News. “The explosion happened whilst he was in the car and how he managed to escape is an utter miracle,” she wrote. “He certainly had some guardian angels looking after him.”

Miriam Berger in Washington and Rachel Pannett in Sydney contributed to this report.

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