The Metropolitan Police have named British-born Khalid Masood as the man responsible for the terrorist attack in London on Wednesday.

Masood, aged 52, was born in Kent and detectives believe he was most recently living in the West Midlands. Masood was also known by a number of aliases.

"Masood was not the subject of any current investigations and there was no prior intelligence about his intent to mount a terrorist attack," the Metropolitan Police said in a statement.

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"However, 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."

Earlier on Thursday, British Prime Minister Theresa May said police knew the identity of the attacker, who was shot dead after he went on a car-and-knife rampage at Parliament on Wednesday. May says he was once investigated for extremist links but was considered a peripheral figure.

Video: British MP gives account of incidents at parliament

The development comes as Britain's Parliament resumed work Thursday in a spirit of defiance as police broadened their investigation into a terror attack that has shaken the country and resulted in eight arrests so far.

"We are not afraid and our resolve will never waver in the face of terrorism," said Ms. May on Thursday. "We know that democracy and the value it entails will always prevail. This was an attack on free people everywhere."

On Thursday morning, Islamic State group said through its Aaamaq news agency that the London attacker was a 'soldier of the Islamic State'.

Flags around Westminster Palace flew at half-mast and security was tightened as Members of Parliament arrived. Some areas around Parliament remained cordoned off as police continue investigating Wednesday's attack.

Late Thursday, police said a 75-year-old man injured in the attack had died of his wounds, bringing the total number of fatalities to five, including the attacker. Several people remain injured, including 12 Britons, three French citizens, two Romanians, four South Koreans, one German, one Chinese, one Irish, one Italian, two Greeks, two Americans and one person from Portugal.

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London attack: What we know so far about the attack at U.K. Parliament

In photos: Britain's Parliament resumes work in spirit of defiance against terror attack

Related: London terrorist attack renews security fears across Europe

"Terrorism will not defeat democracy," Lindsay Hoyle MP, who is deputy speaker of the House of Commons, told the BBC. "The House must continue, we will not give in to terrorism and today we'll continue. We will be paying tributes later this morning and then the House will continue with its business."

Members held a minute of silence at the start of proceedings for the victims of the attack, which included police officer Keith Palmer, an unarmed member of the Parliamentary security force who was stabbed by the attacker. Another small service was held in front of Scotland Yard, headquarters of the London police force, in honour of Mr. Palmer, a 15-year veteran of the force.

The assault began Wednesday afternoon when a man drove an SUV onto the sidewalk along Westminster Bridge, killing two people and injuring dozens of others. He then crashed the vehicle into a fence alongside Parliament and ran toward the gates leading into the House of Commons. He stabbed a police officer before being gunned down.

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Police said they have arrested eight people in a series of raids in London and Birmingham. All were suspected of preparing terrorist acts, police later confirmed. There have also been reports that the car used in the attack was rented near Birmingham. Mr. Rowley added that the attacker acted alone and was inspired by international terrorism.

"The inquiries in Birmingham, London and other parts of the country are continuing," said Deputy Commissioner Mark Rowley. "It is still our belief – which continues to be borne out by our investigation – that this attacker acted alone and was inspired by international terrorism. To be explicit, at this stage we have no specific information about further threats to the public."

One of the victims was a 43-year old school teacher, Aysha Frade who taught at DLD College and was on her way to pick up her two children. Ms. Frade was described by the principal of DLD College as "highly regarded and loved". Several tourists from France, Korea and Britain were also among the injured.

As dusk fell, hundreds gathered in London's 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.

"I have got a lot of friends and family that work five minutes away from there, so it just makes you think," she said. "It made me angry and sad and I wanted to come here and show that we can still all be here together."

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With files from Associated Press and Reuters