The Duke of Edinburgh is receiving medical attention in hospital for "an infection", Buckingham Palace has said.
A short statement added that Prince Philip is "comfortable" and "responding to treatment", but is not expected to leave London's King Edward VII's Hospital for several days.
His Royal Highness, who celebrated his 99th birthday in June 2020, was admitted to hospital last Tuesday after "feeling unwell".
The Duke of Edinburgh received a visit from the Prince of Wales on Saturday.
Prince Philip has had a life-long connection to the British military, including serving in the Second World War with the Royal Navy and being present in Tokyo Bay when Japan surrendered.
Cover image: PA.