Russell Square police cordon
© Via Twitter/Raheem Kassam
A knife-wielding man attacked people at Russell Square, central London, killing one and injuring at least six. Police apprehended the suspect and are investigating the incident as a possible act of terrorism.

Police were called in response to an ongoing attack at Russell Square, Bloomsbury, in the London Borough of Camden at 10:33pm local time, according to the Metropolitan Police. Upon arrival, officers discovered six people with wounds, with one person later dying from her injuries.

"Up to six people were found injured at the location," police said in a statement. "A female (no further details) was treated at the scene but was pronounced dead a short time later. "Police have also notified that they arrested the suspect after one of the officers took him down using a Taser. The London Ambulance Service was dispatched to the site. Additional police units have been deployed to the area to provide reassurance.

"Terrorism is one possibility being explored at this stage," the official statement added. Police did not mention which other possible motives for the attack are being investigated.

Earlier, Metropolitan Police chief Sir Bernard Hogan-Howe announced that additional armed police would be deployed to patrol London's streets following a wave of terror attacks across Europe.

"I want the public to know that we have substantial resources and a range of tactics that we can call on to protect them," Hogan-Howe said, adding that attack in the UK was a case of "when, not if."

Announcing the start of Operation Hercules, Hogan-Howe and London Mayor Sadiq Khan disclosed that they would increase the number of firearm officers on patrol by 600 to 2,800.

"We will see more armed officers on our streets, but there is no reason to be alarmed," Khan said. "All of our police officers are playing their part and working closely with all of our communities to prevent the possibility of an attack."

Update to the above RT article:

The 19-year-old suspect, who had been held in custody at a London hospital, is now in a south London police station having been arrested on suspicion of murder.

Upon arrival, officers discovered six people with wounds, with a woman in her 60s later dying from her injuries.

She was a US citizen, the London Assistant Police Commissioner says.

Spanish, Israeli, Australian and British citizens were injured in the attack, Sky News reports.

"Terrorism is one possibility being explored at this stage," the official statement added.

"Early indications suggest mental health is a significant factor in this case and that is one major line of inquiry," police said in a follow-up release.

"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."