The assailant who carried out a deadly attack outside Parliament on Wednesday was born in Britain, Prime Minister Theresa May told the House of Commons Thursday.

"What I can confirm is that the man was British-born and that some years ago he was once investigated by MI5 in relation to concerns about violent extremism," she told lawmakers.

"He was a peripheral figure," May said, adding that "he was not part of the current intelligence picture."

The prime minister went on to say that there had been no prior intelligence of his plot to carry out an attack on the Westminster Bridge and Parliament.

The militant "Islamic State" (IS) group claimed responsibility for the attack later on Thursday, saying the attacker was one of its "soldiers," according to the IS Aamaq news agency.

The British Parliament reopened on Thursday, one day after the deadly attack that took place outside the Palace of Westminster. MPs and police observed a somber minute of silence to remember the victims.

Arrests made in police raids

Prime Minister May also confirmed that police carried out raids in Birmingham and London as part of the investigation into the attack, arresting a total of eight people.

Earlier on Thursday, Mark Rowley, Britain's top anti-terrorism officer, added that authorities believe the attacker "acted alone" and was "inspired by international terrorism."

Police have said they know the identity of the attacker but have not yet named him as investigations into his "motivation and associates" are ongoing. Rowley added that police have "no specific information about further threats to the public."

He also revised the death toll, saying that four people are dead - including the attacker - and that 29 people are currently being treated in hospital for their injuries. Seven of those wounded are in critical condition.

A knife-wielding man plowed a car into a crowd of pedestrians on London's Westminster Bridge and stabbed a policeman outside the British Parliament on Wednesday. The assailant was shot shortly after stabbing the officer.

Police reported earlier that five people had died and that a total of 40 people were wounded.

Details on victims emerge

One German national was wounded in the attack, Prime Minister May told Parliament on Thursday. Another 12 Britons, three French children, two Romanians, four South Koreans, one Pole, one Irish national, one Chinese, one Italian, one American and two Greeks required hospital treatment.

Earlier, police said the victims of the attack include 48-year-old Keith Palmer, the policeman who was stabbed, and two members of the public - a woman in her mid-40s and a man in his mid-50s. The attacker is the fourth dead.

The three French high-school students, aged between 15 and 16, were on a school trip to London with fellow students from Brittany. French Foreign Minister Jean-Marc Ayrault traveled to the British capital to visit them in hospital and visit Parliament. 

One of the Romanian victims was a woman who was rescued from the River Thames, into which she fell after the attacker's vehicle plowed through pedestrians on Westminster Bridge. Romanian officials said that the woman was in London to celebrate her boyfriend's birthday.

The woman sustained serious injuries to her head and lungs while her boyfriend suffered a fractured foot, Romanian Ambassador Dan Mihalache told Realitatea TV late on Wednesday.

'We are not afraid'

May honored the police and hailed the everday actions of people who went about their lives in London, saying it was proof that the attack failed to break the spirit of Britons.

"It is in these actions - millions of acts of normality - that we find the best response to terrorism - a response that denies our enemies their victory, that refuses to let them win, that shows we will never give in," May told Parliament.

Several Londoners appeared to echo the prime minister's sentiment to defiantly carry on with their lives. The Tower Hill Underground station, known for writing a quote of the day for busy travelers to ponder as they rush through the city, posted a picture of today's quote on Twitter: "The flower that blooms in adversity is the rarest and most beautiful of them all."

They added the hashtags "London is open" and "We are not afraid."

Queen Elizabeth II also offered her condolonces to victims of the attack after postponing her visit to open the new headquarters of London's Metropolitan Police on Thursday.

 "My thoughts, prayers and deepest sympathy are with all those who have been affected by yesterday's awful violence," she said in a message to police.

Sadiq Khan, the mayor of London, said a candlelight vigil for the victims will be held tonight at 6:00 p.m. GMT (UTC) in Trafalgar Square.

rs/se (AP, AFP, dpa, Reuters)