A man was arrested by British police on Tuesday after he approached the gates of Buckingham Palace and threw items "suspected to be shotgun cartridges" into the grounds of the palace, London's Metropolitan Police said.
"The man has been arrested on suspicion of possession of an offensive weapon," police said in a statement.
The arrest comes as police and security services prepare for King Charles' coronation on Saturday, which is expected to see large crowds line the streets of London and heads of state from around the world attend the formal coronation ceremony.
Buckingham Palace said neither the king nor his wife Camilla were at the palace at the time of the incident.
The statement said officers had detained the man and taken him into custody. It also said cordons had been put in place after the man was found to have a suspicious bag.
"There have been no reports of any shots fired, or any injuries to officers or members of the public," Chief Superintendent Joseph McDonald, said.
"Officers remain at the scene and further inquiries are ongoing."
British media reported that neither Charles, 74, or his wife Queen Consort Camilla, 75, were at the palace at the time.
Buckingham Palace officials declined to comment.
The Mall, leading to Buckingham Palace, has been closed off to traffic in preparation for Saturday's coronation, which is the first to take place in Britain for 70 years.
Thousands of ceremonial troops will take part in a procession from Buckingham Palace to Westminster Abbey as part of the coronation, with huge crowds expected.
The security operation to protect the route to and from the abbey -- dubbed Operation Golden Orb -- is one of the biggest in recent years.
It will include rooftop snipers and undercover officers, as well as airport-style scanners, sniffer dogs and a no-fly zone over central London.
