Updated | London mass stabbing victim was US citizen

A knife attack in Russell Square left a woman dead and five other people injured, with police confirming mental illness and the possibility of a terror motive. Police later added that the attacker was a 19-year-old Norwegian national of Somali origin, but they have so far not found any evidence of radicalisation.

The incident took place near the British Museum just after 10:30pm on Wednesday.

The woman, in her 60s, was treated at the scene but was pronounced dead a short time later. Police sources have confirmed that the woman was a US citizen. Another woman and four men suffered “various injuries” in the attack, London police said in a statement early on Thursday morning. They later added that those attacked were British, American, Australian and Israeli.

The man was arrested minutes after police arrived on the scene when officers fired an electric stun gun at him. The suspect was taken to hospital where he remained in police custody.

Police said mental health seemed to be a “significant” factor in the incident.

As detail emerged, the decision was made to have the counter-terrorism command involved in the investigation.

In a statement shortly after 3:30am on Thursday, Mark Rowley, an assistant commissioner in the Metropolitan police and Britain’s most senior counter terrorism officer explained the suspected motives.

“Early indications suggest mental health is a significant factor in this case and that is one major line of inquiry. But of course, at this stage, we should keep an open mind regarding motive and consequently terrorism as a motivation remains but one line of inquiry for us to explore,” he said.