Security in London remains on a high state of alert in the build-up to the coronation of King Charles III on Saturday, after a man was arrested and a controlled explosion took place outside Buckingham Palace on Tuesday evening.

Speaking about the incident, which is not being treated as terror-related, Metropolitan Police deputy assistant commissioner Ade Adelekan said how the man had approached police asking to see a soldier, and when told that he could not, he began to throw shotgun cartridges over the palace gates.

Having been detained within seconds, he was found to be in possession of a knife, but not a firearm. He then told police officers that his rucksack should be handled with care, before it was blown up.

The incident occurred shortly after Charles had hosted Australian Prime Minister Anthony Albanese at the palace, but he was not on the premises at the time.

"Officers worked immediately to detain the man and he has been taken into police custody," said Chief Superintendent Joseph McDonald.

"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."

The Daily Mail newspaper reported that the man was a dog breeder who had traveled down from the north of England, but said claims he had shouted threats against the king had not been verified. He is understood to have undergone a mental health assessment and been judged fit to be interviewed by the police.

DAC Adelekan has described the coronation, from a policing point of view, as "the event of a lifetime", with the security plan, known as Operation Golden Orb, being "one of the most significant security operations that the (Metropolitan Police) has led".

British police officers are not routinely armed, and Sky News reports that around 9,000 non-specialist officers will be deployed on the day, in addition to 2,500 others with specialist roles such as firearms and close protection, meaning there will be more than 11,500 officers on duty for the event that will draw dignitaries from all over the world, and be watched by a global audience.

ITV News reports that police are considering using facial recognition technology this weekend in a bid to pick up individuals who may pose a threat to safety around the coronation.

Airspace over London will be restricted on Friday and Saturday, and a representative for the London police service, known as the Met, said that there were currently no specific threats, but that the force "won't stand for anyone committing criminal acts in the name of protest" and if anyone tried, the police "will come down on them swiftly".

DAC Adelekan said he wanted the coronation weekend to be one to remember for everyone in London. "We want Londoners and visitors coming to the city to enjoy this historic and momentous occasion safely and securely," he said. "The weekend promises to be a spectacular celebration and the Met Police is honoured to be policing such an internationally-important event right across the capital."