Police in London on Tuesday arrested a man allegedly armed with a knife and accused of throwing suspected shotgun cartridges into the grounds of Buckingham Palace.

The arrest, at about 7:00 pm (1800 GMT), comes just days before King Charles III’s coronation, which will be attended by global royalty and world leaders amid a massive security operation..

The Metropolitan Police said officers also conducted a controlled explosion on a suspicious bag the man was carrying “as a precaution”. It later added that it was not treating the matter as terrorism-related at this time.

The man has been arrested on suspicion of possession of an offensive weapon after he was searched and a knife was found, the London force said in an update some three hours after the incident.

“Officers worked immediately to detain the man and he has been taken into police custody,” Met Police chief superintendent Joseph McDonald said in a statement.