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Scotland Yard has confirmed the knife attack inside Leytonstone Tube station tonight is being treated as a terrorist incident.

Police were called to the station just after 7pm to reports of a stabbing and other people being threatened with a knife.

It is claimed a suspect shouted "this is for Syria" during the attack which left one man with serious stab wounds and two others with minor injuries.

The Met said the man's injuries are not believed to be life threatening at this stage.

A man was arrested and taken to an east London police station where he remains in custody. Police confirmed a Taser was used by officers before the arrest.

Tonight, police revealed counter terrorism detectives were now leading the investigation.

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.

"I would appeal to anyone who was in the vicinity of Leytonstone underground station earlier this evening at around 7pm who saw anything suspicious to call the anti-terror hotline on 0800 789 321.

"Anyone who may have captured video or photographic footage of the incident is also urged to make contact with the Counter Terrorism Command via the Anti Terror hotline".

Horrific images circulating on Twitter show a pool of blood on the floor near the ticket barriers and a confrontation in the station.