A man stabbed three people at an east London Tube station, and authorities say they are investigating the attack as a terrorist incident.<br />The assailant, believed to be 29, was subdued with a stun gun and arrested Saturday night, London's Metropolitan Police said.<br />One man, 56, suffered serious injuries, but they're not considered life-threatening, police said.<br />Two others had minor injuries in the attack.<br />Police are looking into reports that the suspect yelled, "This is for Syria," during the attack, said Chioma Dijeh, a spokeswoman for the Metropolitan Police.<br />"We are treating this as a terrorist incident," said Cmdr. Richard Walton, head of the Metropolitan Police Counter Terrorism Command.<br />"I would urge the public to remain calm but alert and vigilant.<br />The threat from terrorism remains at severe, which means that a terrorist attack is highly likely."
