A man was stabbed in the ticket hall at Leytonstone station this evening by another man who witnesses say shouted “This is for Syria” as he slashed his throat.
Another three are thought to have been injured.
The Met Police said its counter-terrorism command unit is now investigating the incident.
Police said they used a taser on the suspect as he threatened others with a knife, before they managed to arrest him.
The victim was rushed to hospital in a serious condition with multiple stab wounds, paramedics said.