In photos: Mourning for London

The death toll from Wednesday's attack on the heart of Britain's democracy grew to five as police said one of the injured, a 75-year-man, had died in hospital after his life support was withdrawn.

That number included the attacher Khalid Masood, 52, who was shot dead by police.

During five minutes of mayhem in the heart of London on Wednesday, Masood sped across Westminster Bridge in a car, mowing down pedestrians. He then ran through the gates of the nearby parliamentary precinct and fatally stabbed an unarmed policeman, Keith Palmer, before being shot dead.

"He will be deeply missed. We love him so much," Palmer's family said in a statement. The 48-year-old was married with a five-year-old daughter.

About 40 people were injured, of whom some were in critical condition. May visited some of them, her spokesman said. The casualties included 12 Britons, three French children, two Romanians, four South Koreans, one German, one Pole, one Chinese, one American and two Greeks, Prime Minister Theresa May said.

Candles burn on Westminster Bridge the day after an attack in London. Photo by Reuters/Darren Staples

People attend a vigil in Trafalgar Square the day after an attack in London. Photo by Reuters/Darren Staples

Floral tributes are seen in Westminster the day after an attack in London. Photo by Reuters//Hannah McKay

A baby holds a bunch of flowers at a vigil in Trafalgar Square the day after an attack in London. Photo by Reuters/Darren Staples

People attend a vigil in Trafalgar Square the day after an attack in London. Photo by Reuters/Stefan Wermuth

A woman holds a placard at a vigil in Trafalgar Square the day after an attack in London. Photo by Reuters/Hannah McKay

The Brandenburg Gate is illuminated with the colors of the British flag to show solidarity with the victims of the recent attack in London, in Berlin, Germany. Photo by Reuters/Fabrizio Bensch

People light candles at a vigil in Trafalgar Square the day after an attack in London. Photo by Reuters/Stefan Wermuth

Britain's Home Secretary Amber Rudd listens as London Mayor Sadiq Khan speaks at a vigil in Trafalgar Square the day after an attack in London. Photo by Reuters/Hannah McKay

A woman looks at floral tributes laid in Westminster the day after an attack in London. Photo by Reuters/Hannah McKay

People light candles at a vigil in Trafalgar Square the day after an attack in London. Photo by Reuters/Hannah McKay

People attend a vigil in Trafalgar Square the day after an attack in London. Photo by Reuters/Stefan Wermuth

Flowers left outside New Scotland Yard after a minute's silence. Photo by Reuters/Neil Hall

Police officers salute during a minute's silence outside New Scotland Yard. Photo by Reuters/Neil Hall

Police officers hold flowers given to them by well wishers in Westminster. Photo by Reuters/Hannah McKay

Queen Elizabeth released a message saying: "My thoughts, prayers and deepest sympathy are with all those who have been affected by yesterday's awful violence."

U.S. tourist Kurt Cochran was named as one of the dead in a Facebook post by family member Shantell Payne.

"With 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," Payne wrote.

Her post said Cochran's 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.

Since the attack in London, police have raided a number of addresses across the city, arresting five men and two women on suspicion of preparing terrorist acts.

The attack was the deadliest in Britain since 2005, when 52 people were killed by Islamist suicide bombers on London's public transport system.