Live updates on the Russell Square attacks have now ended for the day but our main news story will continue to be updated throughout the evening.

We'll be back at 08:00 on Friday with the latest videos, news, sport, travel and weather for London.

Shyam Sanghani who runs Imperial News and Gifts right opposite the attack scene said: "You don't expect it to happen. It's so sad.

"We had more armed police being announced yesterday and then this today - it's scary and it makes you think. We've been here a long time and to have two incidents is awful. This is our home." 

• A man targeted six people with a knife in Russell Square, central London, at about 22:30 last night
• An American woman, believed to have been in her 60s, was fatally stabbed. Matthew Barzun, US ambassador to the UK, described the news as "heartbreaking" in a tweet, adding: "My prayers are with all the victims and their loved ones."
• A 19-year-old man, a Norwegian national of Somali origin, has been arrested on suspicion of murder. He emigrated from Norway in 2002.
• Two women and three men suffered "various injuries" in the attack, with two remaining in hospital and the other three discharged. None is in a life-threatening condition. Those injured are Australian, American, Israeli and British.
• The victims were selected at random in a "spontaneous" rampage and no evidence has been found that the attack was motivated by terrorism, Scotland Yard said.
• London mayor Sadiq Khan has called for the public to remain "calm and vigilant".

A 19-year-old man has been arrested on suspicion of murder after a US citizen in her 60s was killed and five other people were injured in a knife attack in Russell Square.

Emma and Mark Pigdon visiting the capital from County Durham were their way back from the theatre when they saw the incident unfolding.

Emma said: "We just saw a woman lying on the street. She looked like she had a pattern on her clothes but it turned out to be blood.

"She was a really small lady, really slight, which made me think she was a teenager. We were shocked when we later heard she was in her 60s."

Philippa Bagley saw the aftermath of the attack in London's Russell Square yesterday.

She was staying at the nearby Hotel President and was outside having a cigarette when she saw what she thought was the result of a road accident.

"It just looked like someone had collapsed or come off their bike. I thought it was maybe a motorcycle accident. It didn't look frantic at all but just Lots of people standing around."

Image source, PA

In his press conference earlier, Assistant Commissioner Mark Rowley, said: "This attack will cause concern.

"So as a precautionary measure we have increased the number of officers out on the streets today and that will continue for as long as we need it to.

"I want everyone who is out and about in London today - our residents; businesses or visitors - to know that the Met is totally committed to doing everything we can do to protect you."

Image source, Getty Images

As the day has gone on, members of the public and representatives of local businesses have being laying floral tributes at the scene where the American woman was killed. 

No personal messages were attached to the flowers, some of which carried general messages of condolences.

Image source, PA

Image source, PA

Councillor Sarah Hayward, leader of Camden Council, the authority which covers Bloomsbury, said: “I am deeply saddened by the terrible incident in Russell Square. My thoughts are with the victims, and their families and friends.

“I’ve spoken to Metropolitan Police Commissioner Sir Bernard Hogan-Howe this morning who has updated me on the investigation. I would like to thank the police for their response to this difficult situation and acknowledge the hard work they are now engaged in to investigate the incident. They have the council’s full support. “The safety of everyone who lives or works in Camden, as well as those who are visiting, is our priority. While tragic incidents such as last night’s are rare, I do urge people to report anything suspicious to the police. Please remain calm while we continue to work with the police, other emergency services and the Mayor of London to reassure our communities.”

The Jewish Chronicle

An Israeli tourist was injured in the stabbing attack, external in central London.

A spokesperson for the embassy of Israel confirmed one of the victims was an Israeli woman on holiday in the UK visiting friends and family.

Norwegian Police say they are helping their Met Police counterparts with their investigation into last night's murder and stabbings.

They can confirm, however, that the suspect is a Norwegian citizen but who left Norway in 2002, when he was about five years old.

Image source, PA

This morning officers searched an address in north London and will search another in south London. 

Mark Rowley, Britain's most senior counter-terrorism officer, said: "I emphasise that so far we have found no evidence of radicalisation that would suggest the man in our custody is in any way motivated by terrorism.

"The suspect is a Norwegian national, of Somali origin. I stress though that all the work we have done so far does not suggest that those factors in his background are relevant to the motivation for his actions."

In a speech in Dagenham earlier, Labour leader Jeremy Corbyn said: "We should express our sympathies to the family of the poor woman who was stabbed to death last night in Russell Square and thank the police for the action they took very quickly to make the area safe."

"I would urge no-one to speculate on the reasons or the causes for it, but to be grateful that we have efficient emergency services that were able to bring about some safety for that area at the present time," he said.

As well as revealing details about the suspect and victims, Assistant Commissioner Mark Rowley has revealed more details about the investigation:

"The investigation is fast paced and we are making urgent progress.

"While the investigation is not yet complete, all of the work that we have done so far increasingly points as having been triggered by mental health issues.

"At this time we believe this was a spontaneous attack and that the victims were selected at random."

He also described how police had "searched addresses in north London" and we will search another in south London.

"I emphasise that so far we have found no evidence of radicalisation that would suggest that the man in our custody is in any way motivated by terrorism," he added.

Mr Rowley said the injured victims "are not in a life threatening condition".

The 19-year-old who has been held on suspicion of murder is "a Norwegian national of Somali origin", Assistant Commissioner Mark Rowley said.

The Met have confirmed the woman killed in last night's attack was from the US.

Assistant commissioner for specialist operations Mark Rowley said the other five injured are from UK, USA, Israel and Australia.