The Duke of Edinburgh is “comfortable and responding to treatment” for an infection.
But the Queen’s husband is not expected to leave hospital for several days, Buckingham Palace said.
Philip, 99, was admitted to King Edward VII’s Hospital in London last Tuesday evening as a precautionary measure after feeling unwell, and walked into the building unaided.
In a short statement, the 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.”
Prince Edward said in a TV interview that his father was doing well.
He told Sky News: “He’s a lot better, thank you very much indeed and he’s looking forward to getting out, which is the most positive thing so we keep our fingers crossed.”
Asked whether Philip was frustrated to be in hospital, Edward laughed and replied: “Just a bit. I think that gets to all of us, and then, you can only watch the clock so many times and the walls are only so interesting.”
He added: “We’ve had some brilliant and lovely messages from all sorts of people and we really appreciate that and so does he, I’ve been passing them on. It’s fantastic, thank you.”