The Princess of Wales has postponed months of engagements after undergoing abdominal surgery that will require two weeks in hospital and a lengthy recovery.

Kensington Palace said her procedure at a private London clinic on Wednesday (local time) was planned and had been successful.

No details of the surgery were given, but a palace spokesman said the condition was non-cancerous.

“The surgery was successful and it is expected that she will remain in hospital for 10 to 14 days, before returning home to continue her recovery.”

Heir to the throne Prince William, 41, will not carry out any official duties while Kate, 42, is in hospital or immediately after she is discharged.

Less than two hours later Kensington’s Palace announcement, it was announced that the King would also undergo a “corrective procedure” to treat an enlarged prostate and had also postponed some duties.

Buckingham Palace revealed that the 75-year-old monarch would go to hospital next week, but said his condition was benign.

“In common with thousands of men each year, the king has sought treatment for an enlarged prostate,” the palace said in a statement.

The Princess of Wales was admitted to The London Clinic. Photo: Getty

The two royals have both appeared to be in good health. They were last seen in public on Christmas Day when the royal family made their annual visit to a church service near the King’s Sandringham home in eastern England.

Royal watchers have speculated that the princess’ condition is serious given the time she will remain in hospital, the length of the expected recovery and the “tone” of the statement.

On medical advice, she is unlikely to return to public duties until after Easter, the palace statement said.

“The Princess of Wales appreciates the interest this statement will generate,” the statement said.

“She hopes that the public will understand her desire to maintain as much normality for her children as possible; and her wish that her personal medical information remains private.”

The Princess of Wales and the King at the royal family’s Christmas Day church service. Photo: Getty

Kensington Palace said it would provide updates on Kate’s progress only when there was “significant new information to share”.

“The Princess of Wales wishes to apologise to all those concerned for the fact that she has to postpone her upcoming engagements.

“She looks forward to reinstating as many as possible, as soon as possible,” the palace said.

Few details of Kate’s condition were made public, as is usual with the royals who regard medical issues as a private matter.

Kate and William have three children — Princes George and Louis and Princess Charlotte. She spent four days in hospital in 2012 suffering from severe morning sickness while pregnant with eldest son George.

The BBC notes that two royal health announcements on the same day is very unusual, but the King reportedly had upcoming engagements that would be affected.

The King was also keen to share information to encourage other men experiencing symptoms to have their conditions checked.

An enlarged prostate seems to be a “normal part of ageing in men”, but the degree of enlargement and severity of symptoms can vary, according to the Australian Urology Associates website.

The gradual enlargement of the prostate compresses the urethra and causes obstruction to urine flow, with symptoms such as weak urine flow, urgency and nocturia (getting up from sleep to urinate).

It is not cancer, and does not turn into cancer.

Treatment options include medications to relax or shrink the prostate or surgery to remove the obstructing prostate tissue.

-with AAP