Prince Philip will have to miss out on Diamond Jubilee festivities for the next few days.
Queen Elizabeth's husband -- who will turn 91 on Saturday -- was rushed to London's King Edward VII Hospital Monday after developing a bladder infection.
"He is currently receiving treatment," a Buckingham Palace spokesperson tells Us Weekly. "He will remain in hospital under observation for a few days."
His hospital stay means the Duke of Edinburgh will have to skip out on Monday evening's Diamond Jubilee concert -- the latest in a string of engagements honoring the 60th anniversary of his wife's ascension to the throne. "He is understandably disappointed at missing this evening's Diamond Jubilee concert and tomorrow's engagement," the palace spokesperson adds.
A source tells Us that although Philip's hospitalization comes on the heels of Sunday's Thames River Pageant -- during which the royal family spent time on their boat in cold, blustery weather -- "[his health scare] is not linked to yesterday's [event]."
"The Duke was feeling unwell and so a doctor was called as a precautionary measure," the source says. "The Queen will continue to attend Jubilee celebrations."