A stabbing at a London Underground station is being treated as “terrorist incident,” the London police said Saturday.

The London police counterterror command said in a statement that it is investigating the incident at Leytonstone Underground station in east London in which a man was threatening people with a knife at around 7 p.m.

Police said one man sustained serious knife injuries but that they were not expected to be life-threatening. Two others suffered minor injuries.

A suspect was under arrest. A stun gun was used to subdue him, police said.

“We are treating this as a terrorist incident,” said Commander Richard Walton, head of the Metropolitan Police’s Counter Terrorism Command. “I would 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 authorities did not say why they believe the incident was terror-related.

Police asked witnesses, especially those who have photos of videos of the incident, to contact them.

The stabbing comes only days after Britain’s Parliament gave overwhelming approval to authorizing the military to conduct airstrikes on Islamic State group targets in Syria.

Several British newspapers reported that eyewitnesses to the incident said that the man shouted “This is for Syria,” but police declined to comment on any reports.

Has anyone figured out we (the world) are under attack?