The British royal family’s official website is at the centre of a “Russian hacking” mystery.

A cyber crook from Russia has claimed to be behind an “attack” on the royals’ site after the royal.uk domain started displaying an error message stating Gateway time-out Error code 504 on Sunday.

Hacker ‘KillMilk’ has been bragging on encrypted messaging app Telegram – notorious for being used by terror groups – of their apparent successful hack of the page.

They wrote it was an “attack on paedophiles...” with a sad face emoji on the messaging site, with a picture of King Charles used in the background.

Check Host, a website that covers sites that have gone down across the web, commented about the supposed Russian hack: “Incredible if real!”

The site showed a list of countries where the royal website was down, including the UK, UAE, Ukraine, US, Turkey, Russia, Japan, Poland and others.

But a source told The Sun Online: “The website wasn’t hacked. It was a denial of service attack.

“This is when a site is bombarded with access requests. The royal household’s systems and content was not accessed.

“We can’t say yet who was responsible.”

KillMilk is the leader of a Russian hacking collective that calls itself Killnet.

They recently announced on Telegram the establishment of ‘Black Skills’ – a name thought to have been inspired by mercenary companies in Russia.

The supposed attack comes after the late Queen Elizabeth stepped up defences against hackers after learning the royal family were a high-profile target.

It’s thought the family’s site went down shortly after 10.20am on Sunday and lasted around two hours.

The Sun Online added IT experts for the royals worked on “fully restoring the website”, but said Buckingham Palace declined to comment when approached for comment.

In July 2021, Queen Elizabeth – who died aged 96 in September 2022 – ordered increased online security following a report from her cyber security experts who warned there was a high rather than medium risk of unauthorised access to royal household data.

Experts also warned international cyber terrorists were a potential threat to King Charles’ coronation in May.