London stabbing rampage: What we know so far

An American woman was killed and five others wounded in a knife attack in London on Wednesday night. The rampage, which comes amid heightened vigilance over radicalization and mass terror attacks in Europe, prompted authorities to increase London's armed police presence on the streets.

Here's what we know so far about the attack:

-Police said there is no evidence that the assailant, a 19-year-old Norwegian national of Somali origin had any links to terrorism.

-The woman who died is a US citizen in her 60s. Another woman and four men were treated in hospital for stabbing injuries. Three were later discharged. None of the victims, who came from Australia, Britain, Israel and the US, received life threatening injuries.

-London Metropolitan Police Assistant Commissioner Mark Rowley said that evidence collected so far "increasingly points" to the attack being "triggered by mental health issues".

-The attack in London's Russell Square — a busy tourist area — appeared to be "spontaneous" and the victims "selected at random," according to police.

-Police were called to the scene of the stabbings at around 10:33pm Wednesday. An officer reportedly used a Taser to subdue the assailant before police formally arrested him.

-The accused stabber emigrated from Norway in 2002, according to Norwegian police who are assisting local law enforcement in its investigation.

-London Mayor Sadiq Khan released a statement urging Londoners to "remain calm and vigilant." "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," Khan said.

-Islamist militants hit London with coordinated suicide bombings on July 7, 2005, killing 52 people. One of the bombs detonated on a bus close to Russell Square. Since then, dozens of plots have been foiled and there have been smaller-scale attacks, such as the beheading of an off-duty soldier by militant Islamists in a London street in May 2013.

-A man who attacked passengers at a London underground train station in December was jailed for life earlier this month. The judge said the attacker was suffering from paranoid schizophrenia at the time of the offense but may have been motivated by events in Syria.

Reuters contributed reporting to this article.