London (CNN) -- Prince Philip, husband of Britain's Queen Elizabeth II, underwent "exploratory" abdominal surgery Friday at a London hospital, a Buckingham Palace spokesman said.
The Duke of Edinburgh was admitted to the hospital Thursday and is expected to stay there for up to two weeks, according to the palace statement.
He is being treated "following abdominal investigations."
The surgery took place Friday, the palace said. It went as planned, and Philip is "progressing satisfactorily."
The 91-year-old is set to celebrate his birthday Monday.
He had been expected to accompany the queen as she formally opened the British Broadcasting Corporation's rebuilt central London headquarters, Broadcasting House, on Friday.
She toured the broadcaster's main newsroom and radio studios, and made a live appearance on the BBC news.
The prince showed no signs of illness Thursday at a presentation at Buckingham Palace, according to the Press Association. The news agency reported Philip was joking and laughing with guests at a ceremony where the queen made him a member of the Order of New Zealand.
After the presentation, the queen and Philip hosted a garden party in the grounds of Buckingham Palace as part of celebrations for the 60th anniversary of the queen's coronation.
He and other members of the royal family also attended a service at Westminster Abbey on Tuesday to mark the anniversary.
Philip left Greece a year after he was born there, following the 1922 overthrow of his uncle King Constantine I. Despite his roots in that country, he has a mixed ancestry and, like his wife, is a great-great-grandchild of Britain's Queen Victoria.
A Royal Navy veteran, he met Elizabeth in 1939 and married her in November 1947. They have four children.
In addition to his royal and military duties, Philip has served as president of the World Wildlife Fund and the International Equestrian Foundation.
Philip has had a number of documented health problems in recent years, including treatment for a blocked coronary artery in December 2011 and a hospitalization in June 2012 for a bladder infection. He was admitted again to a hospital -- this time in Scotland -- for treatment of the latter ailment two months later.
CNN's Max Foster contributed to this report.