The Duke of Edinburgh is being treated for an infection and is "comfortable and responding to treatment" but is not expected to leave hospital for several days, Buckingham Palace has said.
In a short statement, Buckingham Palace said: "The Duke of Edinburgh remains at King Edward VII's Hospital where he is receiving medical attention for an infection.
"He is comfortable and responding to treatment but is not expected to leave hospital for several days."
Philip was admitted to King Edward VII's hospital in London last week as a precautionary measure and walked unaided into the medical centre.
The Duke of Edinburgh's son Prince Charles visited him in hospital over the weekend and was pictured looking upset upon leaving the visit.
He is the first member of the royal family to visit Philip during the Duke's week stay in hospital.
The duke, who turns 100 on June 10, is in hospital for an undisclosed reason, although it is not coronavirus-related.
Philip has suffered a number of ailments over the years, including being treated for a blocked coronary artery in December 2011 and a bladder infection in June 2012, forcing him to miss the Queen's Diamond Jubilee celebrations.
Exploratory surgery on his abdomen followed in June 2013 and he began to use hearing aids by 2014, aged 93.
He later pulled out of a Battle of Jutland anniversary event in June 2016 citing a minor ailment which was followed soon after by his retirement from public duty in 2017.
He spent four nights at King Edward Hospital in December 2019, where he was treated for a "pre-existing condition" and was later discharged on Christmas Eve.
The Duke was then driven to Sandringham and spent Christmas with the Queen.