British head-of-state King Charles III left a private London hospital on Monday three days after undergoing a procedure for an enlarged prostate.

The 75-year-old monarch, dressed in a suit and a black overcoat, waved to crowds as he and Queen Camilla emerged from the clinic and climbed into a waiting car.

Buckingham Palace said Charles, who spent three nights at the hospital, had rescheduled his forthcoming engagements while he recuperates.

"His Majesty would like to thank the medical team and all those involved in supporting his hospital visit, and is grateful for all the kind messages he has received in recent days," a statement read.

Charles became king upon the death of his mother, Queen Elizabeth II, on September 8, 2022, and has generally enjoyed good health, barring injuries from polo and skiing.

A palace announcement on January 17 that he had been diagnosed with the condition was a break with a tradition of relative secrecy about the health of the monarch.

Charles wanted to publicise his own case to raise awareness about the condition, which is common in men aged over 50 and affects urination.

Symptoms include a frequent need to pass water and difficulty in fully emptying the bladder.

Charles's daughter-in-law, Catherine, Princess of Wales had been at the same central London hospital after undergoing abdominal surgery.

Her Kensington Palace office said earlier on Monday that she had been discharged and would recuperate at the home she shares with Charles's son and heir Prince William, and their three children.