London Parliament attacker was British-born, had been investigated in past

LONDON — The knife-wielding terrorist who killed three people outside the U.K. Parliament was British-born and was once investigated by security services over "violent extremism," Prime Minister Theresa May said Thursday.

The attacker was known to police as "a peripheral figure" and "was not part of the current intelligence picture," she told the House of Commons.

She was speaking yards from the scene of Wednesday's carnage, which also injured 29 others. An American and three French children on a school trip were among those wounded.

The dead included a police officer and a mother-of-two who was hit by a bus as she ran to safety.

The terrorist plowed a 4x4 rental car into people walking on Westminster Bridge before crashing it a railing outside the House of Commons. He later fatally stabbed the cop before being gunned down by armed officers.

"It is still believed that this attacker acted alone and the police have no reason to believe that are imminent further attacks on the public," May said.

However, police overnight raided at least six properties in cities including Birmingham — where the culprit's vehicle was rented from Enterprise — and London, making eight arrests.

"Clearly our investigation is ongoing ... and is focused on his motivation, his preparation and associates," Metropolitan Police Acting Deputy Commissioner Mark Rowley told reporters early Thursday.

Amaq, the media unit of ISIS, released a statement describing the London attacker as "a soldier of the Islamic State" although it cited no evidence for the claim.

Charlie Winter, a senior research fellow at the London-based International Centre for the Study of Radicalisation and Political Violence (ICSR), said the claim framed the atrocity as inspired, not directed, by ISIS. "This distinction is hugely important," he wrote.

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ISIS has claimed responsibility after other attacks, including the Istanbul nightclub rampage on New Year's Eve and the Nice promenade truck massacre last July, without providing evidence.

Rowley said that seven of the wounded were still in critical condition on Thursday.

One of the dead was identified as Aysha Frade, 43, a mother-of-two who was hit by a bus as she fled from the vehicle on Westminster Bridge. She was on her way to pick up her children from school.

The small Spanish town of Betanzos, where her family lives, declared three days of mourning.

Lawmakers observed a minute's silence in tribute to slain police Constable Keith Palmer, 48, who died despite efforts to revive him by doctors and a passing government minister.

One of the wounded was a tourist who plunged from the bridge into the River Thames. The woman, who was in the city to celebrate her boyfriend's birthday, suffered serious head injuries and has badly damaged lungs, Romanian diplomat Dan Mihalache told Realitatea TV, according to The Associated Press.

May said the attacker's name would be released "when operational considerations allow."

She said he had been investigated "some years ago" by the MI5 domestic intelligence service "in relation to concerns about violent extremism."

May added: "He was a peripheral figure. The case is historic. He was not part of the current intelligence picture. There was no prior intelligence of his intent or of the plot."

The prime minster told lawmakers that "the working assumption is that the attacker was inspired by Islamist ideology."

May also paid tribute to government minister Tobias Ellwood, who tried to save the dying police officer. "Yesterday we saw the worst of humanity but we will remember the best," she said.

Mayor Sadiq Khan invited Londoners to an evening vigil and promised "business as usual" in the capital.

"London is a city that's been resilient in the face of terror attacks in the past," he told NBC News. "People are returning to work today ... we're not going to allow a terrorist to divide our communities or change our way of life."

More police officers than usual were on patrol as the Metropolitan Police aimed to provide "reassurance."

Westminster Bridge remained cordoned off and the surrounding streets — normally thronged with commuters — were eerily quiet except for the buzz of a police helicopter.

Defense Minister Michael Fallon described Wednesday's atrocity as a "lone-wolf attack" but said investigators were still checking "whether other people were involved."

He added: "London is getting back to work. London has seen this before and is taking it on the chin."