Saudi Crown Prince Sultan bin Abdul Aziz has died, a palace announcement on state television said on Saturday, throwing his brother Prince Nayef into line to succeed King Abdullah as leader of the key oil producer.

The crown prince, aged around 86, also the minister of defence and aviation, had been in the United States since mid-June for medical treatment. He was operated on in July but no information was released on his health conditions since then.

A half brother of King Abdullah, Sultan had spent long periods abroad for health reasons.

He died while the monarch himself, 87, remains in hospital in Riyadh, a week after he had an operation on his back.

The second in line to the succession, Prince Nayef, 78, another half-brother of King Abdullah who holds the portfolio of interior becomes the crown prince.

He was named second deputy prime minister in March 2009.

Prince Sultan's funeral will take place on Tuesday after his body is repatriated from the United States.