The attacker who killed three people near parliament in London before being shot dead was named on Thursday as a 52-year-old British-born man, Khalid Masood, who was once investigated by MI5 intelligence officers over concerns about violent extremism.
Islamic State claimed responsibility for the attack in a statement issued by its Amaq news agency, but did not name Masood and gave no details. It was not clear whether the attacker was directly connected to the jihadist group.
Police said Masood was born in the county of Kent in southeast England and was most recently living in the West Midlands region of central England.
โMasood was not the subject of any current investigations and there was no prior intelligence about his intent to mount a terrorist attack,โ the Metropolitan Police said in a statement.
โHowever, he was known to police and has a range of previous convictions for assaults, including GBH (grievous bodily harm), possession of offensive weapons and public order offences.โ
Prime Minister Theresa May told parliament the attacker had once been investigated by the MI5 intelligence agency over concerns about violent extremism, but had been a peripheral figure.
Police said Masood had never been convicted of a terrorist offence. His first conviction was in 1983 for criminal damage and his last one in December 2003 for possession of a knife.
During five minutes of mayhem in the heart of London on Wednesday, Masood sped across Westminster Bridge in a car, ploughing into pedestrians. He then ran through the gates of the nearby parliamentary precinct and fatally stabbed an unarmed policeman before being shot dead.
Police arrested eight people at six locations in London and Birmingham in the investigation into the attack, which May said was inspired by a warped Islamist ideology. All were suspected of preparing terrorist acts, police later confirmed.
The Enterprise rental car company said the vehicle used had been rented from its Spring Hill branch in Birmingham, which is in the West Midlands.
About 40 people were injured, of whom 29 remained in hospital on Thursday evening, seven in critical condition. May visited some of the wounded, her spokesman said.
The bloodshed took place on the first anniversary of attacks that killed 32 people in Brussels, and resembled Islamic State-inspired attacks in France and Germany where vehicles were driven into crowds.
The dead were Masood, two members of the public, and Keith Palmer, the 48-year-old policeman stabbed by Masood.
โHe will be deeply missed. We love him so much,โ Palmerโs family said in a statement. He was married with a five-year-old daughter.
A minuteโs silence was held in parliament and outside police headquarters on Thursday morning. A police Twitter account said it had been held at 0933 GMT because 933 was the shoulder number on Palmerโs uniform, but that tweet was later deleted and police released a different number.
As dusk fell, hundreds gathered in Londonโs Trafalgar Square in a vigil to remember the victims. With traffic diverted away, volunteers handed out candles in an eerie silence.
Helen Pallot, 26, from just outside London, was holding a bunch of flowers she planned to lay nearby.
โI have got a lot of friends and family that work five minutes away from there, so it just makes you think,โ she said. โIt made me angry and sad and I wanted to come here and show that we can still all be here together.โ
Speaking at the United Nations in New York, British Foreign Secretary Boris Johnson urged Internet providers and social media networks to do more to curb extremist propaganda.
โTheyโve got to look at the stuff thatโs going up on their sites, theyโve got to take steps to invigilate it, to take it down where they can,โ he said.
Wednesdayโs attack was the deadliest in Britain since 2005, when 52 people were killed by Islamist suicide bombers on Londonโs public transport system. Police had given the death toll as five, but on Thursday morning revised it to four.
The casualties included 12 Britons, three French children, two Romanians, four South Koreans, one German, one Pole, one Chinese, one American and two Greeks, May said.
Queen Elizabeth released a message saying: โMy thoughts, prayers and deepest sympathy are with all those who have been affected by yesterdayโs awful violence.โ
US tourist Kurt Cochran was named as one of the dead in a Facebook post by family member Shantell Payne.
โWith a heavy heart I must pass the sad news of our beautiful brother, father, husband, son and friend Kurt Cochran, he could not overcome the injuries he received in the London terror attacks,โ Payne wrote.
Her post said Cochranโs wife, Melissa Payne Cochran, was in hospital with a broken leg and rib and a cut on her head.
The couple were in Europe to celebrate their 25th wedding anniversary.
US President Donald Trump paid tribute to Cochran in a tweet, calling him โa great Americanโ.
Many have been shocked that the attacker was able to cause such mayhem in the heart of the capital equipped with nothing more than a hired car and a knife.
โThis kind of attack, this lone-wolf attack, using things from daily life, a vehicle, a knife, are much more difficult to forestall,โ Defence Secretary Michael Fallon told the BBC.
Three French high-school students on a school trip to London were among the injured. French Foreign Minister Jean-Marc Ayrault met some of their fellow students near the hospital where they were being treated. Their lives were not in danger.