A 21-year-old man was arrested at a residential address in east London on Friday on suspicion of terrorist acts, the Metropolitan Police said.
The suspect has not been identified but the police said that he was detained under the Terrorism Act 2000 and was taken to a south London police station where he remains in custody. He is suspected of the commission, preparation, or instigation of an act of terrorism.
Police officers have been carrying out a search at an east London address, the statement added.