THE stabbing of three people at a Tube station by a man wielding a machete is being treated as a terrorist incident, police have said.

The man reportedly shouted "This is for Syria" after he launched the attack at Leytonstone station in east London.

Video clips circulated on social media by eyewitnesses showed a large pool of blood near the barriers and a stand-off between the suspect and police officers in the ticket hall. People can see be seen running away through the station amid the panic.

There were reports from people in the station that the man had shouted "this is for Syria' and "all your blood will be spilled".

Warning: Video below contains graphic content

Commander Richard Walton, who leads the Met's Counter Terrorism Command, said: "We are treating this as a terrorist incident. 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 Met confirmed they had arrested a man after discharging a Taser gun.

A spokesman said: "One victim is in a serious condition with multiple stab wounds and it is believed up to two others may also have been injured."

A spokeswoman from London Ambulance Service said: "We treated a man for stab wounds. He was taken as a priority to hospital escorted by the doctor from London's Air Ambulance. "