LONDON • An American woman was killed and five people injured by a man with suspected mental health issues who went on a rampage with a knife in central London. Police said there was no evidence that the attack was terrorism related.

Armed police were called late on Wednesday after a Norwegian man of Somali origin started to attack people with a knife in London's Russell Square, an elegant park near the site of a 2005 suicide bombing.

Mr Xavery Richert, 22, a French tourist staying in a youth hostel on the square, said: "I was buying a beer when I heard a woman shouting and being chased by a man.

"I thought it was a bag snatching. She was not hurt. I came out for a cigarette, I went back, there were firefighters, police, and then I saw the body under a sheet. You could see only the feet sticking out."

The victim, in her 60s, was treated at the scene but pronounced dead a short time later.

Another woman and four men were treated in hospital, though three of them were later discharged. Nationals from Australia, Britain, Israel and the US were among those hurt.

"All of the work we have done so far increasingly points to this tragic incident as having been triggered by mental health issues," said London Metropolitan Police Assistant Commissioner Mark Rowley yesterday.

"We believe this was a spontaneous attack and that the victims were selected at random," said Mr Rowley, ruling out terrorism after initially saying terrorism was a line of inquiry.

The 19-year-old suspect was detained after police used a Taser electric-shock gun on him. He was later formally arrested on suspicion of murder.

The square sits in the heart of London's university area and is close to landmarks such as the British Museum.

London mayor Sadiq Khan, the first Muslim mayor of a major Western capital, called for vigilance and urged Londoners to report anything suspicious to the police, who increased their presence in the city.

Just hours before the Russell Square attack, London's police chief said that he would deploy an additional 600 armed officers across the capital to protect against attacks.

London counter-terrorism police chiefs have previously warned that the Islamic State in Iraq and Syria was seeking to radicalise vulnerable people with mental health issues to carry out attacks. In some operations, police commanders have taken advice from specialist psychologists.

Militants hit London with coordinated suicide bombings on July 7, 2005, killing 52 people. One of the bombs detonated on a bus close to Russell Square.

Since then, dozens of plots have been foiled and there have been smaller-scale attacks, such as the beheading of an off-duty soldier by extremists in a London street in May 2013.

A man who attacked passengers at a London underground train station in December was jailed for life this month. The judge said the attacker was suffering from paranoid schizophrenia at the time of the offence but may have been motivated by militancy in Syria.

Separately, security agencies in Paris have circulated a photo of an Afghan asylum seeker on suspicion that he might be plotting an attack on the capital, a police source said yesterday.

Police did not have a name for the Afghan, the source said, and no active manhunt was under way. Metronews reported that the man had been in France for the past two months.

France has been under emergency rule since militant gunmen and suicide bombers killed 130 people in Paris in November.

REUTERS, AGENCE FRANCE-PRESSE