A 19-year-old youth was arrested on Friday for terror-related offences after a suspicious item was found on a Tube train in North Greenwich area.
The man was nabbed by officers of Scotland Yard's counter terrorism command, assisted by armed colleagues in a street in north London.
Officers discharged a taser during the arrest but no firearms were used.
"The 19-year-old man was arrested on suspicion of the commission, preparation and instigation of terrorism acts, under Section 41 of the Terrorism Act 2000. He has been taken to a London police station where he remains in custody," a Metropolitan Police statement said.
The incident on the London Underground railway system took place yesterday when British Transport Police (BTP) were called to the North Greenwich Underground Station after train staff reported finding a suspicious item on a train travelling eastbound on the Jubilee Line.
The station was evacuated while specialist officers from the Metropolitan (MeT) Police Service and BTP attended and made the item safe by carrying out a controlled explosion.
"The item is currently being forensically examined and we await the results of that examination. The Met and BTP have been working tirelessly since the item was found to follow up all potential leads. Officers are keeping an open mind regarding any possible motive. They are not looking for anyone else in relation to this investigation at this stage, the Met statement said.
Scotland Yard encouraged the public to remain "vigilant and alert" at all times and report anything suspicious to police. They have ordered extra officers to patrol potential transport targets across London after the suspicious item was found.
Media reports indicated that the suspicious item was an abandoned bag full or wires.