The Duke of Edinburgh has been admitted to a London hospital for an exploratory operation.
Buckingham Palace says Prince Philip, who is 91, was admitted to the London Clinic following abdominal investigations and is expected to stay in the hospital for up to two weeks.
The operation will take place on Friday under general anaesthetic. the BBC reports it is a planned, not an emergency, admittance.
On Monday, Prince Philip pulled out of an engagement for the Royal National Institute of Blind People after becoming unwell ahead of last week's service marking 60 years since the Queen's coronation.
He attended the service at Westminster Abbey on Tuesday and was present at a garden party attended by the Queen at Buckingham Palace on Thursday afternoon.
Also on Thursday, the Queen presented Prince Philip with the highest honour in New Zealand's honours system during a ceremony at Buckingham Palace, AAP reports.
The prince was named an additional member of the Order of New Zealand in June last year to mark the Queen's Diamond Jubilee.
He received the Order of New Zealand badge previously worn by the Queen Mother, who was an additional member of the order from 1990 until her death in 2002.