Updated February 6, 2024 at 12:08 PM ET

LONDON — King Charles III has been diagnosed with cancer, Buckingham Palace has announced.

"During The King's recent hospital procedure for benign prostate enlargement, a separate issue of concern was noted. Subsequent diagnostic tests have identified a form of cancer," Buckingham Palace's statement said Monday.

It did not specify what type of cancer but said the king began treatments Monday.

Doctors advised the 75-year-old monarch to postpone public-facing duties, the statement said, but he will continue state business and paperwork.

"The King is grateful to his medical team for their swift intervention, which was made possible thanks to his recent hospital procedure," the statement said.

Prince Harry flew in from California to be with his father, after the king personally gave the news about his diagnosis to all of his children and siblings.

Messages of support began to stream in from across the United Kingdom and its allies.

"Like everyone else, we're shocked and sad, and just all our thoughts are with him and his family," British Prime Minister Rishi Sunak told the BBC on Tuesday. "Thankfully, this has been caught early and now everyone will be wishing him, that he gets the treatment that he needs and makes a full recovery. That's what we're all hoping and praying for."

President Biden told reporters on Monday, "I'm concerned about him."

Sunak is expected to continue his weekly meetings with the king as he undergoes outpatient treatment.

The news comes less than a year and a half into Charles' reign, following the death of his mother Queen Elizabeth II.

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