A woman has been killed and five others injured in a knife attack in Russell Square, central London.
Police were called to the scene at 22.33 BST on Wednesday to reports of a man armed with a knife assaulting people at Russell Square, Camden.
Officers discharged a Taser whilst arresting attacker, and took him to hospital, where he remains under armed guard.
Police described the suspect as a 19-year-old Norwegian national of Somali origin, and said there was no evidence of radicalisation.
The woman killed in the attack was described as being in her 60s, and two of the other people injured remain in hospital.
The Met said “mental health is a significant factor” and Homicide and Major Crime Command are leading the investigation, supported by officers from the Counter Terrorism Command.
Assistant Commissioner Mark Rowley, from the Metropolitan Police, said:
“This was a tragic incident resulting in the death of one woman and five others being injured. Early indications suggest that mental health was a factor in this horrific attack. However we are keeping an open mind regarding the motive and terrorism remains one line of inquiry being explored.
“As a precautionary measure, Londoners will wake up this morning to notice an increased presence on the streets of officers, including armed officers today. We would urge the public to remain calm, alert and vigilant.
In a statement, London Mayor said:
“The safety of all Londoners is my number one priority and my heart goes out to the victims of the incident in Russell Square and their loved ones.
“I have spoken with the Commissioner, and the Assistant Commissioner, who have assured me that our police officers are working extremely hard to investigate exactly what has happened and to keep the rest of us safe. A man was arrested at the scene. Police have spoken to him and are seeking to establish the full facts including motives for this attack.
“I urge all Londoners to remain calm and vigilant. Please report anything suspicious to the police. We all have a vital role to play as eyes and ears for our police and security services and in helping to ensure London is protected.
“Our police officers are doing an incredibly difficult job on our behalf and they have my full support.”