LONDON, UNITED KINGDOM - King Charles III on Wednesday met British Prime Minister Rishi Sunak in person for their weekly audience for the first time since announcing his cancer diagnosis, UK television channels reported.

The meeting at Buckingham Palace came after the 75-year-old monarch attended a church service at his country residence of Sandringham in eastern England on Sunday.

The king appeared to be in good spirits, quipping after Sunak said he was looking well that "it's all done by mirrors".

"We're all behind you. The country is all behind you," Sunak said.

"I've had so many wonderful messages and cards. It's reduced me to tears most of the time," Charles said.

The king announced on February 5 that he had been diagnosed with cancer, and left his London Buckingham Palace home shortly afterwards to undergo treatment at Sandringham.

The diagnosis was made after a "separate issue of concern was noted" and investigated while he was being treated for a benign enlarged prostate.

His diagnosis came just 17 months into his reign following the death of his 96-year-old mother, Queen Elizabeth II, on September 8, 2022.