Breaking: Buckingham Palace has gone into lockdown days out from King Charles' coronation.

Buckingham Palace has gone into lockdown after a man allegedly threw what was "suspected to be shotgun cartridges" into the palace grounds.

The man was arrested after he approached the gates of the palace and threw the items into the area.

"The man has been arrested on suspicion of possession of an offensive weapon," police said in a statement.

#BREAKING: Buckingham Palace is in lockdown and a man has been detained after throwing what is believed to be "shotgun cartridges" into palace grounds. @Brett_McLeod #9News pic.twitter.com/WqvuVLXVnr

— 9News Australia (@9NewsAUS) May 2, 2023

According to the BBC, a controlled explosion was carried out by specialists as a precautionary measure. 

The arrest comes as police and security services prepare for King Charles' coronation on Saturday, which is expected to result in large crowds lining the streets of London and heads of state from around the world attending 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," said Chief Superintendent Joseph McDonald.

"Officers remain at the scene and further enquiries are ongoing."

- With AAP.

Feature Image: Belinda Jiao/Getty.