King Charles has been diagnosed with a form of cancer, BBC reports.

It is not prostate cancer, but was discovered during his recent treatment for an enlarged prostate.

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The type of cancer has not been revealed, but according to a Buckingham Palace statement, the King began "regular treatments" on Monday.

Buckingham Palace says the King "remains wholly positive about his treatment and looks forward to returning to full public duty as soon as possible".

He will postpone his public engagements and it is expected other senior royals will help to stand in for him during his treatment.

No further details are being shared on the stage of cancer or a prognosis.

Although he will pause his public events, the King, 75, will continue with his constitutional role as head of state.

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He was seen at a church service in Sandringham on Sunday, where he waved to crowds.

He had a prostate procedure at a private London hospital more than a week ago.

The King had chosen to go public about his prostate treatment, with the aim of encouraging more men to get prostate checks, the palace said at the time.

He was said to have been delighted to have raised awareness about the issue, with the NHS website reporting a surge in issues about prostate conditions.