Guy would have been shot about 20 times if this was in the US.
A man reportedly screamed 'this is for Syria' before allegedly slashing a person's throat and attacking up to three people.Police were called to Leytonstone station after reports of a stabbing in the ticket hall on Saturday at around 7pm.
Sources told the Telegraph one person has been seriously injured and a second was also hurt.
Officers Tasered a man at the scene.
A video apparently of the incident and posted on Twitter shows a large pool of blood spattered across the ticket hall as the alleged knifeman is Tasered by a police officer.
Terrified passengers, some with children, can be seen running across the east London Tube station away from the scene.
A Met Police spokesman said: "Police were called at 19:06hrs on Saturday, 5 December, to reports of a stabbing at Leytonstone underground station. The male suspect was reportedly threatening other people with a knife.
"Met officers attended the scene. A man was arrested at 19:14hrs and taken to an east London police station where he remains in custody.
"A Taser was discharged by one of the Met officers.
"Officers from British Transport Police are now dealing with the incident at the scene. We are aware of one man having sustained serious stab injuries. We await details of any other injuries."
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 were called at 7:09pm to reports of an assault at Leytonstone underground station.
"We sent a number of resources to the including our joint response unit, an incident response officer, an ambulance crew and London's Air Ambulance to the scene.
"We treated a man for stab wounds.
"He was taken as a priority to hospital escorted by the doctor from London's Air Ambulance. "
In the video the knifeman approaches and gesticulates at people in the station.
As they approach him he lashes out with his knife and appears to slash one of them in the neck area.
The police can be heard to shout "drop it, drop it you fool, drop it".
Moments later a uniformed police officer arrives on the scene and fires his Taser at the man.
Terrified passengers, some with children, can be seen running across the east London Tube station away from the scene.
