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 November 13 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.