The diagnosis came shortly after the 75-year-old monarch was treated for an enlarged prostate.

LONDON, Feb. 5 (Xinhua) -- Britain's King Charles III has been diagnosed with cancer and has started receiving treatment, Buckingham Palace announced on Monday.

The diagnosis came shortly after the 75-year-old monarch was treated for an enlarged prostate.

"His Majesty has been treated for benign prostate enlargement. It was during this intervention that the separate issue of concern was noted and subsequently diagnosed as a form of cancer," a Palace spokesperson said.

A statement from Buckingham Palace said the King has "today commenced a schedule of regular treatments, during which time he has been advised by doctors to postpone public-facing duties."

According to the statement, throughout the period, the King will continue to "undertake State business and paperwork as usual."

The monarch "remains wholly positive about his treatment and looks forward to returning to full public duty as soon as possible," it said.

"His Majesty has chosen to share his diagnosis to prevent speculation and in the hope it may assist public understanding for all those around the world who are affected by cancer," it added.

British Prime Minister Rishi Sunak has issued a statement, saying he wishes "His Majesty a full and speedy recovery."

"I have no doubt he'll be back to full strength in no time and I know the whole country will be wishing him well," he said.

The King traveled from Sandringham in Norfolk to London on Monday morning to begin treatment as an outpatient. He was seen at a church service in Sandringham on Sunday, where he waved to crowds.

The monarch is at home in London this evening, according to Sky News. No further details are shared on the stage of the cancer or a prognosis.