Prince Philip, husband of Britain's Queen Elizabeth II, is expected to undergo "an 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 will likely take place Friday unless the medical advice changes, the palace spokesman said.
The 91-year-old is set to celebrate his birthday Monday.