A man was detained by armed police outside the Palace of Westminster on Friday.
The man, in his 30s, was arrested on suspicion of possessing a knife, the Metropolitan Police said. There were no reports of any injuries, BBC reported.
The bearded man, wearing black trousers and a grey sweatshirt, was seen being held against the fence with his arms behind his back by a police officer.
The incident is not thought to be terror related and the Carriage Gates entrance to Parliament was closed, the report said.