UPDATE: 9:15 p.m. EST -- Police early Monday, London time, filed attempted murder charges against a 29-year-old man who went on a stabbing rampage in the Leytonstone Underground Station. Muhaydin Mire was in custody at Westminister Magistrates' Court.

UPDATE: 12:33 p.m. EDT -- The British Transport Police announced Sunday they are employing additional security measures in the wake of the stabbing, and asked the public to remain calm and continue using public transportation in their normal fashion.

"The safety of the traveling public remains our top priority. In addition to our usual specialist response teams, last week we launched Project Servator deploying even more highly visible police patrols designed to identify and deter terrorism,” assistant chief constable Mark Newton said in a statement.

“Following the incident last night, we are now deploying still more officers in this role. They involve both uniformed and plain-clothed officers, supported by other resources, such as armed officers, police dogs, a network of CCTV cameras, and the thousands of rail staff we work alongside.”

Original story:

Detectives are investigating a violent and seemingly unprovoked knife attack at London's Leytonstone subway station -- which left one man seriously injured -- as a “terrorist incident,” London's Metropolitan police said in a statement Sunday. The 29-year-old suspect was arrested after being Tasered by police Saturday evening, with witnesses saying he shouted, “This is for Syria.”

“As a result of the information received at the time from people who were at the scene and subsequent investigations carried out by the Counter Terrorism Command, I am treating this as a terrorist incident,” Richard Walton, commander of the Met's Counter Terrorism Command Division. “I would continue to urge the public to remain calm but alert and vigilant. The threat from terrorism remains at severe, which means that a terrorist attack is highly likely.”

The man attacked the 56-year-old victim -- punching and kicking him before knocking him to the floor and pulling out a 3-inch knife, witnesses said, before shouting threats at others in the subway station. The victim suffered “serious” knife wounds but is expected to survive. Graphic video footage recorded by bystanders shows a large amount of blood spread over the floor of the Leytonstone station.

The attack comes weeks after the Islamic State terrorist group claimed responsibility for a series of attacks in Paris that killed 130 people. That attack was followed by a mass shooting in San Bernardino, California, that killed 14 people and, while police have yet to identify a motive, the FBI is investigating it as a terrorist incident.

“Whilst this is clearly a serious incident and the mayor's thoughts are with the victim, it would be inappropriate to comment further at this stage on what is an ongoing investigation,” a spokesman for London mayor Boris Johnson said in a statement. “The incident, and the swift and professional response of the officers involved, remind us of the dangers faced by the police every single day in their efforts to protect Londoners and keep the city safe.”