One woman has been killed in a mass stabbing in Russell Square, central London that has left five others injured.
Armed Metropolitan Police officers arrested a 19-year-old man shortly before 11pm on Wednesday evening after he was subdued with a Taser. Authorities are investigating possible links to terrorism, but say that mental health may play a "significant factor".
The injured victims were taken to hospital, and their condition remains unknown. The female victim, who police said was in her 60s, died shortly after officers arrived at the scene.
"This was a tragic incident resulting in the death of one woman and five others being injured," said Assistant Commissioner Mark Rowley. "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."
The suspect is being held in police custody at a London hospital.
Mr Rowley said Londoners should expect heightened police presence – including armed officers – as a precautionary measure. According to eyewitnesses, a forensics team has erected a tent along Southampton Row.
The Metropolitan Police Service's Homicide and Major Crime Command is currently investigating the scene at Russell Square – a busy area near the British Museum and University College London.
Fears of terrorist connections come in the wake of high profile attacks by lone men in Nice, France, and Orlando, Florida, where seemingly mentally disturbed attackers also claim allegiance to Isis.
No connections to terrorism have been confirmed regarding this particular attack.