A man was arrested at the gates of Buckingham Palace in London on Tuesday evening as he threw suspected shotgun cartridges into the palace grounds, Scotland Yard said.
The incident, just four days before the Coronation ceremony of King Charles III and Queen Camilla, involved Metropolitan Police specialist officers conducting a controlled explosion "as a precaution".
The suspect at the scene remains under arrest on suspicion of possession of an offensive weapon and cordons were put in place after the man was also found to be in possession of a suspicious bag.
"Officers worked immediately to detain the man and he has been taken into police custody," said Joseph McDonald, Chief Superintendent of the Met Police.
"There have been no reports of any shots fired, or any injuries to officers or members of the public. Officers remain at the scene and further enquiries are ongoing," he said.
The force said roads that were closed in the wake of the incident have largely reopened and the majority of the cordons have been lifted.
The Met Police is undertaking one of its largest policing operations as it prepares for the historic Coronation procession that will leave the palace grounds and head towards the Abbey on Saturday morning.
Thousands of military personnel have been training for the grand spectacle, involving officers on horseback and foot marching as part of the regal procession through the streets of London.
