Crown Prince Sultan bin Abdul-Aziz Al Saud, the 83-year-old defence minister and first in line of succession to become king of Saudi Arabia, has died.
"With deep sorrow and sadness ... King Abdullah bin Abdulaziz mourns the death of his brother and his Crown Prince Sultan who died at dawn this morning Saturday outside the kingdom following an illness," the Saudi state press agency said.
Prince Sultan's funeral will be held on Tuesday, the statement said.
He was an "important and influential senior prince" who played a key role in relations with the Gulf Cooperation Council, particularly Yemen, said Hussein Shobokshi, a columnist for the Asharq Alawsat newspaper.
"He was always in favour of stability and has always been in touch with various sectors of Yemeni society, tribal, governmental, and he was keen on having ... a smooth political climate that does not affect the kingdom," Shobokshi said.
The death of Prince Sultan raises questions over the succession to the throne in Saudi Arabia
With Prince Sultan's death, his brother Prince Nayef bin Abdul-Aziz, the longtime minister of interior, becomes the most probable candidate to be next in line to rule after King Abdullah.
Analysts believed Sultan had been suffering from a form of dementia, and a March 2009 US diplomatic cable released by WikiLeaks said he was "for all intents and purposes incapacitated".
He received a diagnosis of colon cancer in 2004.
Prince Sultan was the seventh of the 36 sons of King Abdul-Aziz bin Saud, who united and founded Saudi Arabia in 1932. Like Nayef and the deceased former King Fahd, he was a member of the "Sudairi Seven," the powerful alliance of seven surviving sons of Abdul-Aziz and one of his wives, Princess Hissa Al Sudairi.
Prince Sultan served as defence minister for nearly 50 years, the longest term of any Saudi minister, and brought advanced military hardware to the kingdom from the United States and United Kingdom.
Among his sons are Prince Khalid, who has overseen fighting against Yemeni rebels and commanded Arab forces against Saddam Hussein in the first Gulf War, and Prince Bandar, who served as ambassador to the United States between 1983 and 2005.
A changing kingdom?
In 2006, the king formed an Allegiance Council meant to help oversee succession issues. The king has ultimate authority to choose the next crown prince and heir, and it remains unclear how exactly the council will interact with him.
Khaled al-Maeena, editor in chief of the Arab News newspaper in the Saudi capital Riyadh, said that whomever was chosen to succeed Abdullah would need to take into account "new faces" and a changing kingdom.
"It is very important for those who follow now, and the leaders of Saudi Arabia, to take into account, not because of Arab springs or Arab winters, but to take into account that there is a young constituency with different wishes and goals," he said.
Prince Sultan's official birthday in the kingdom is January 5, 1928, but some Western analysts believe he was actually born in 1924.