A 19-year-old man is in police custody after a woman was killed and five people injured in a knife attack in Russell Square in the center of London late Wednesday.
According to police, mental health is a “significant factor” in the attack, but terror motives cannot be excluded.
“Terrorism as a motivation remains but one line of inquiry for us to explore,” Police Assistant Commissioner Mark Rowley said in a statement, AFP reports.
Mayor of London Sadiq Khan on Thursday urged Londoners to remain “calm and vigilant” in the wake of the attack.
Police were called to Russell Square at 10:33 p.m. in response to reports that a man armed with a knife was attacking people. He was arrested six minutes later, after police fired a taser. The man is currently in police custody in hospital.
Two of those who were injured in the attack remain in hospital, while three others have been discharged, London’s Metropolitan Police Service announced on Twitter.
Two people who were injured in the #RussellSquare incident remain in hospital. Three others have been discharged. Further update to follow
— Metropolitan Police (@metpoliceuk) August 4, 2016
The terror threat level in Britain is currently set at the second highest level, severe, with an attack “highly likely.”
On Wednesday prior to the attack, London’s mayor and police commissioner announced an extra 600 armed police officers would patrol the city to protect against terrorism.
Europe has faced a string of terror-related attacks.
In July, Mohamed Lahouaiej Bouhlel drove a truck through a crowd after a fireworks display in Nice, France, killing 84 people, and two men killed a priest in northern France. ISIL claimed the attacks. In Germany, a 17-year-old Afghan refugee injured several people during an ax rampage on a train in July, and a 27-year-old Syrian detonated a bomb outside a bar in Ansbach.
This story has been updated with additional information.