U.K.'s Prince Philip undergoes surgery

Britain's Prince Philip is progressing "satisfactorily" after undergoing exploratory abdominal surgery, Buckingham Palace said Friday.

Philip, 91, was admitted to the hospital on Thursday for the pre-planned procedure. He is expected to stay there for up to two weeks.

The palace said Friday the operation has taken place and that the results will now be analyzed.

"At this early stage he is progressing satisfactorily," the palace said in a brief statement. It did not provide further details.

The 91-year-old was admitted to the London clinic -- a private hospital and longtime favorite for the royals -- after attending a garden party at Buckingham Palace. Philip appeared relaxed as he mingled with guests and told jokes at the party.

Officials have not released details about his condition but indicated he had had tests earlier in the week.

He had pulled out of one event this week but later attended a service at Westminster Abbey to mark the 60th anniversary of the coronation of his wife, Queen Elizabeth II.

The queen continued with her working schedule Friday, officially opening the revamped and expanded BBC broadcasting facilities.

She seemed cheerful most of the time but at other times looked somber and tired.