London: A man was being held in custody Sunday after three people were stabbed at a London Underground train station in an attack police were treating as a ‘terrorist incident’.

One eyewitness shouted ‘You’re no Muslim’ at the suspect as he was pinned down by police officers at the suburban Leytonstone station, amateur video footage showed, while a pool of blood was seen in the ticket hall.

Sky News reported that eyewitnesses had said the lone suspect spoke of Syria and had ‘apparently shouted ‘this is for Syria’,’ though no witnesses were quoted.

Police could not confirm this when contacted by AFP and it is not evident from video footage circulating online.

The attack Saturday came at the end of a week in which the British parliament voted to extend air strikes on the Islamic State jihadist group (IS) from Iraq into Syria.

The stabbings also come less than a month after the 13 November jihadist rampage in Paris, claimed by IS, which killed 130 people.

London police said one man sustained serious knife injuries in the east London attack, but they were not thought to be life-threatening, while two others sustained minor injuries.

Britain’s Counter-Terrorism Command is investigating.

‘We are treating this as a terrorist incident,’ CTC leader Commander Richard Walton said in a statement.

‘Stupid idiot’

Amateur video showed a pool of blood and bloody footprints at the Tube station ticket gates.

Shouts are heard as the suspect is seen remonstrating with people before swinging at one of them.

Some Tube-users continued on their way while others hurried from the scene.

Footage shows officers shouting ‘Drop the knife!’ and firing Taser electric stun guns, one of which connects.

‘Who is this idiot?’ one onlooker said of the suspect, adding: ‘Yes! Stupid idiot,’ after the man is Tasered.

Officers shout ‘Put the knife down!’ and ‘Drop it now!’ at the stunned man, who did drop the short-bladed knife as he quivered on the ground.

On his front, the man was handcuffed behind his back while another officer pinned him down with his knee and passers-by were told to get back.

One man at the scene then shouted at the suspect: ‘You ain’t no Muslim, bruv! You’re no Muslim, bruv! You ain’t no Muslim!’

Eyewitness Khayam told the BBC that when the suspect was taken to a police van, ‘I saw pedestrians shouting at him... one pedestrian tried to throw a bottle.’

He said one victim was taken out on a vertical stretcher.

Witness Michael Garcia, 24, a financial analyst from Leytonstone, said he had seen ‘a guy, an adult, lying on the floor with a guy standing next to him brandishing a knife of about three inches (7.5 centimetres)’, the BBC reported.

‘He was screaming ‘go on, then, run’ to everyone else. He was pacing back and forth next to the guy on the floor.’

Terror threat level ‘severe’

Police said they were called at 7:06pm (1906 GMT) Saturday to reports of a number of people being stabbed at the Central Line station.

‘The male suspect was reportedly threatening other people with a knife,’ Scotland Yard police headquarters said.

‘A man was arrested at 7:14pm and taken to an east London police station where he remains in custody.’

Walton said: ‘I would urge the public to remain calm, but alert and vigilant.’

Britain’s national terror threat level was raised in August 2014 to severe, the second-highest of five levels, meaning an attack is considered highly likely.

The London Ambulance Service said one patient was treated for stab wounds at the station and was taken to hospital escorted by a doctor.

A large section of the Central Line in east London remained shut early Sunday.

Leytonstone station was sealed off with police tape and an officer in a forensic outfit was seen taking photographs of the scene.

The station is decorated with mosaics depicting film scenes by director Alfred Hitchcock, who hails from Leytonstone, as does football icon David Beckham.

Police will have 24 hours at the very least to question the suspect.

Suspects can be held without charge for up to 14 days if arrested under the Terrorism Act.