LONDON - Counterterrorism police in Britain on Sunday investigated a stabbing at a London Underground station in which a man brandishing a knife injured two people and reportedly said "This is for Syria."
Police arrested a 29-year-old man late Saturday and said they are treating the "violent unprovoked knife attack" at East London's Leytonstone subway station as a "terrorist incident."
Richard Walton, chief of Scotland Yard's counterterrorism command, said the decision was made because of information received from witnesses and subsequent police investigations. The force said it was searching a residential address, but declined to say whether they were looking for other suspects.
British media widely reported that the suspect linked his actions to Syria after the attack. The claim could not be independently verified, but the incident comes just days after Parliament approved British airstrikes on Islamic State group targets in Syria.
Authorities in Britain, as in many other European countries, are already on edge after Islamic extremist attacks in Paris last month left 130 people dead. The last extremist attack in Britain was in May 2013, when two British-born, al-Qaeda-inspired extremists stabbed an off-duty soldier to death on a busy London street.
In Saturday's attack, one man suffered serious knife injuries and was in the hospital in stable condition. Another man received minor injuries, while a woman was threatened but not hurt.
Video shot by witnesses at the scene showed a pool of blood on the station's floor as the suspect was seen lunging at several police officers who tried to subdue him. He was then pinned down after a stun gun was used.
One bystander can be heard shouting at the suspect: "You ain't no Muslim, bruv." The phrase, using slang for "brother," was quickly picked up by Twitter users who turned it into a trending hashtag to show their contempt for the suspect and extremism.
Salim Patel, who runs a shop at the station, told reporters the suspect punched and kicked a man before stabbing him.
"I saw the guy attacking the victim, punching him so hard. The victim was screaming 'please somebody help me! Help!' " he said. "Then the attacker started kicking him on the floor . . . the attacker took a knife out and started stabbing him as he lay on the floor."
The suspect remained in custody at a police station Sunday.
Britain's national terrorism threat level remains at "severe," meaning that authorities believe an attack is highly likely.