King Charles III has warned of the challenges disinformation and other "hostile online activity" pose to trust and security in the digital age.

The comments, made in a letter to the National Cyber Security Centre (NCSC) to mark its 10th anniversary, spoke of "malicious actors" continuing to "evolve their tactics by using automated technologies".

"From threats to our international order, to the need to balance the risks and opportunities of powerful new technologies, strong cyber security is fundamental to making the online environment safer and more resilient," he wrote.

Last month, the King warned AI executives of the "existential dangers" posed by the technology falling into the wrong hands.

In the letter published on Saturday by NCSC, the King praised the government agency. He said its achievements over the past decade have included defending the country against cyber attacks, safeguarding democratic institutions and protecting "the critical infrastructure upon which daily life depends". "You have built resilience across our public services, businesses and communities, equipping us all to prosper in our ever-evolving digital world," the monarch added.

The King said he was "acutely aware" that much of the work done by the NCSC cannot be praised publicly and that he was filled with "profound gratitude".

The NCSC was established in 2016 as part of the Government Communications Headquarters to protect the UK against cyber threats.

Earlier this week, the NCSC offered assistance to online shopping store Asos after customers received a notification from its app sent by hackers, the BBC understands.

The high profile hack made global headlines on Tuesday when cyber criminals used Asos's own app system to send a pop up notification to potentially millions of people.

Asos said it was investigating "unauthorised activity" involving third-party platforms. The company told its customers that hackers are in possession of detailed profiles of potentially millions of the company's users including names, addresses, phone numbers, emails, customer numbers and dates of birth.

It issued the update after BBC News told the retailer it had been contacted by cyber criminals who said this week's breach went beyond the "basic contact details" Asos previously said might have been accessed.

The letter from the King to NCSC came after he spoke to AI executives at Dumfries House in Ayrshire last month on how the tech can be used to benefit security.

The meeting followed a series of recent warnings from people inside the industry about the rapidly evolving capabilities of advanced or "frontier" AI models and the regulation needed to keep them in check. "Those who have created these technologies are now increasingly warning that AI risks developing darker capacities - perhaps even to take life," the King told the executives.

He said there seemed to be an "urgency" in "adequately considering the existential dangers of such technologies falling into the wrong hands, and being used in potentially catastrophic ways". "The task before you is not merely to advance technology, but to ensure that it remains firmly in the service of humanity, community and the natural world," he told the group.