An 18-year-old was arrested on Saturday in connection with the terror attack on a London Tube train that left 29 people injured.
The man was detained in the port area of Dover by Kent Police over the Friday morning rush hour attack at the Parsons Green station in southwest London, BBC reported.
The Islamic State claimed responsibility for the attack.
Metropolitan Police Deputy Assistant Commissioner Neil Basu said the arrest was “significant”, but the terror threat level remains at “critical”.