A burial ceremony was set for the holy city of Mecca, where the 88-year-old King Abdullah gathered with royal family members and international envoys. Abdullah has now outlived two appointed successors from among the elderly group of sons of Saudi's founding monarch, King Abdul-Aziz.
Health issues increasingly preoccupy the ruling inner circle in Saudi Arabia and show the vivid contrast between a leadership born at the dawn of Saudi's oil-rich age and the current population heavily weighted toward youth -- with more than half under 25 years old.
Saudi authorities have led the efforts in the Western-allied Gulf to counter Arab Spring-inspired calls for reforms, using a combination of crackdowns, intimidation and lavish spending to offer state jobs and handouts. Gulf officials have proposed closer cooperation on security matters, including monitoring social media.
The 78-year-old Nayef, the country's interior minister, was considered wary of even the modest changes brought by King Abdullah, including pledges to allow women to vote and run in the next municipal elections in 2015.
Women activists had planned Sunday to mark the anniversary of a campaign to challenge the ultraconservative kingdom's ban on female driving, but they postponed the protests because of the official mourning period for Nayef.
The leading figure as the next heir to the throne, 76-year-old Defense Minister Prince Salman, also is not viewed as a dynamic reformer willing to confront the behind-the-scenes power center in Saudi Arabia -- the Islamic religious establishment that gives the monarchy its legitimacy to rule.
Later this week, a special council of royal family members is expected to convene to select the next crown prince of OPEC's top oil producer. The wider succession shake-up also will be closely watched.
It opens the possibility that a member of the so-called "third generation" -- the thousands of younger descendants of King Abdul-Aziz -- could move into positions traditionally considered in line for the throne.
In 2010, Salman had spinal surgery and has suffered at least one stroke, leaving him with limited movement in his left arm, said Simon Henderson, a Saudi affairs expert at the Washington Institute for Near East Policy.
The Saudi leadership keeps a tight lid on health-related issues. The cause of the crown prince's death in Geneva was not disclosed.
Nayef left the country in late May for what was described as a "personal vacation" that would include undisclosed medical tests. Earlier this year, he was treated at the Cleveland Clinic in Ohio, but no details have been officially disclosed.
Nayef's predecessor, Prince Sultan, 80, died in October in New York after an unspecified illness.
As interior minister since 1975, Nayef was in charge of internal security forces. He built up his power in the kingdom though his fierce crackdown against al-Qaida after the Sept. 11 attacks in the U.S. and a broader campaign to prevent the growth of Islamic militancy among Saudis.
The 9/11 attacks at first strained ties between the two allies, Saudi Arabia and the U.S. For months, the kingdom refused to acknowledge that any of its citizens were involved in the suicide airline bombings.
Nayef finally became the first Saudi official to publicly confirm that 15 of the 19 hijackers were Saudis. That came in a February, 2002 interview with The Associated Press.
Nayef took a leading role in combatting the al-Qaida branch in Yemen as well. In 2009, al-Qaida militants tried to assassinate his son, Prince Muhammad, who is deputy interior minister and commander of counterterrorism operations.
A suicide bomber posing as a repentant militant blew himself up in the same room as the prince but failed to kill him.