Prince Philip has been hospitalised for a pre-existing condition.
Buckingham Palace confirmed in a statement on Saturday morning the Duke of Edinburgh travelled from Norfolk to the King Edward VII Hospital in London.
The palace said the 98-year-old will be kept under observation for a pre-existing condition. It said his admission is a "precautionary measure".
He will also receive treatment.
This is not his first recent hospitalisation. In 2011 he spent Christmas having surgery for a blocked artery, and in 2012 he was hospitalised with a bladder infection, reports Reuters.
Last year, Prince Philip had his hip replaced, requiring a 10-day stay.
Prince Philip is the husband of Queen Elizabeth II. The couple celebrated their 72nd wedding anniversary in November.
