LONDON (AFP) - Hundreds of people paid tribute in central London on Thursday (March 23) to the victims of a terror attack outside British parliament a day earlier which left three people dead and dozens injured.

London Mayor Sadiq Khan led the tributes in a heavily-policed Trafalgar Square, vowing "Londoners will never be cowed by terrorism" after a 52-year-old British-born man went on the rampage at Westminster.

"The victims were people who came from all corners of our world," he said.

Standing alongside Home Secretary Amber Rudd and Craig Mackey, the acting commissioner of London's Metropolitan Police, Khan lit a candle in an act mirrored by the crowds gathered in the famous square.

A man draped in Britain's Union Jack flag was among those lighting candles placed on sand, while others left flowers in the square.

Messages of defiance were brought to the vigil, including a "Hate will not divide us" sign held by a member of the public and "We are not afraid" written on the ground.

'WE WILL CARRY ON'

Retiree Wendy Scott was among the hundreds of people who came to Trafalgar Square to express her solidarity with victims of the attack.

"We will carry on," she told AFP, before laying a bunch of daffodils in the square.

Naveed Mirza, a Muslim student, said he had received "overwhelming" support since the attack described by police as "Islamist-related terrorism".

"We have come to say how, as Muslims, we unequivocally condemn all the violent actions that took place yesterday," he told AFP.

"People have been coming to us, they have been very supportive telling us we should have nothing to fear," Mirza added.

The Islamic State in Iraq and Syria (ISIS) group claimed one of its "soldiers" was behind the attack in which a British woman, an American man and a London policeman were killed.

The Metropolitan Police held a meeting of faith leaders on Thursday to discuss how to tackle "the discord, distrust and fear that terrorists seek to create".

Police officers in Trafalgar Square were approached by numerous people who offered their condolences for the death of their colleague, who was stabbed to death outside parliament by a man police named as Khalid Masood.

"I told them I'm sorry for your loss and we stand by you for your work," said Anne-Marie Wilson, a 53-year-old charity worker.

"They have lost a brother, it could have been any one of us," she told AFP.

Masood intially drove across Westminster Bridge, ploughing into pedestrians before crashing the car and stabbing police officer Keith Palmer, before being shot by police.

Forty people were injured in total, including two people who are battling life-threatening injuries and five in a critical condition.