London attacker identified as 52-year-old Khalid Masood

Britain's prime minister defiantly declared Thursday that "we are not afraid" even as the Islamic State group claimed responsibility for an attack by a man who plowed an SUV into pedestrians on a London bridge and then stabbed a police officer to death at Britain's Parliament.

In a sweeping speech before the House of Commons, British Prime Minister Theresa May said the man who killed three people Wednesday before being shot to death by police was born in Britain and once came under investigation for links to religious extremism.

British officials named the attacker as Khalid Masood, a 52-year-old with criminal convictions who was living in the West Midlands, which includes the central city of Birmingham.

Police arrested seven people in Birmingham and one in London — five men and three women — on suspicion of preparation of terrorist acts in connection to the Westminster Bridge attack.

Among the homes raided in Birmingham was one Masood lived in until just after Christmas, according to a neighbour.

Iwona Romek, who said she lived for about five months two doors down from Masood, said he had a wife and a young child and appeared like a "normal family man who liked to take care of his garden."

Romek looked with surprise at a photo of the attacker on a stretcher.

"From the face, from the beard -- that is 100 per cent him," she said.

Romek said Masood would walk the child, around 6 years old, to school in the morning, and that he rarely left in the evenings. But one day she saw him packing their belongings in a black van and then they were gone, months after moving in.

May set an unyielding tone Thursday, saluting the heroism of police as well as the bravery of ordinary people in the British capital who simply went about their lives in the aftermath of the attack.

"As I speak, millions will be boarding trains and airplanes to travel to London, and to see for themselves the greatest city on Earth," May told the House of Commons. "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."

Parliament held a moment of silence Thursday morning to honour the slain officer, Keith Palmer, a 15-year veteran of the Metropolitan Police and a former soldier, as well as the other victims.

Then Parliament, which was locked down after the attack, returned to business — a counter to those who had attacked British democracy.

In the 1,000-year-old Westminster Hall, the oldest part of Parliament's buildings, politicians, journalists and parliamentary staff lined up to sign a book of condolences for the victims. Among them was a uniformed policeman, who wrote: "Keith, my friend, will miss you."

Several thousand people crowded London's Trafalgar Square for a memorial on Thursday evening, where three large candles were placed in front of the National Gallery.

People lit candles for those killed and wounded and one woman painted the word "freedom" on her forehead. The crowd was so quiet that the bells of Big Ben, near where the attack occurred, could be heard chiming in the distance.

The rampage was the first deadly incident at Parliament since 1979, when Conservative lawmaker Airey Neave was killed in a car bombing by Irish militants.

People from 11 countries were among the victims, including 12 Britons, four South Koreans, three French, two Romanians, two Greeks, two Irish, two Americans and one person each from Germany, Poland, China and Italy.

Kurt Cochran, a Utah man visiting London with his wife Melissa for their 25th anniversary, was named as among the dead by the Church of Jesus Christ of Latter-day Saints. His wife has been hospitalized in the attack.

U.S. President Donald Trump was among the world leaders offering their condolences.

London has been a target for terrorism many times over past decades and the threat level for the British capital was already listed at severe, meaning an attack was "highly likely."

May said the attack in London targeted "free people everywhere" and declared she had a response for those behind it: "You will not defeat us."