Saudi Arabia's King Fahd died on Monday after years of ill health and a turbulent reign that saw the ultra-conservative Muslim kingdom face up to a wave of deadly Islamic extremism.
His half-brother, Crown Prince Abdullah, who has been de facto ruler for a decade, was anointed his successor at the helm of the oil-rich Gulf state, as widely expected.
Medical sources said that King Fahd, believed to be aged 84, died in hospital at dawn.
State television interrupted programmes to air verses from the holy Koran.
"Prayers for King Fahd bin Abdel Aziz will be held following afternoon prayers tomorrow Tuesday at the Imam Turki bin Abdullah mosque," according to a statement read on state television.
"Members of the family have pledged allegiance to Crown Prince Abdullah bin Abdel Aziz as king over the country," it said.
"Then, King Abdullah bin Abdul Aziz... chose Defence Minister Sultan bin Abdul Aziz as crown prince... and members of the family pledged allegiance to his Excellency."
The king had been admitted to King Faisal Specialist Hospital in Riyadh in late May for "medical tests" and was said to be suffering from respiratory problems caused by pneumonia.
Believed to have been born in 1921, Fahd took charge in 1982 of a vast kingdom which is the world's largest petroleum exporter and holds a quarter of global oil reserves.
He guided Saudi Arabia through the most turbulent era in its history, which saw the kingdom survive two Gulf Wars only to have to confront the menace of Islamic extremism.
Two years of strife perpetrated by Islamic extremists has claimed the lives of 90 civilians, 42 security personnel and 113 militants, according to official figures.
Saudi's alliance with the United States, the cornerstone of Fahd's foreign policy was sorely tested by the September 11, 2001 terror attacks on the United States, in which 15 out of the 19 attackers were Saudi.
Designated as next in line after King Faisal's assassination in 1975, Fahd was in practical terms running the country under the rule of his ailing brother King Khaled from 1975 to 1982.
After the stroke in 1995 confined him to a wheelchair, the king delegated the day-to-day business of government to his half-brother, Crown Prince Abdullah bin Abdul Aziz.
Soon after Fahd's death was announced, Crown Prince Abdullah, who himself is in his 80s, was named the next king.
It was Fahd himself who upheld the Saudi tradition of the crown prince succeeding the monarch by asking Abdullah to run the country after suffering a stroke in 1995.
Saudi Arabia's crown prince has traditionally replaced the king on the monarch's death or abdication, but a law introduced by King Fahd opened the door for the succession to skip a generation.
The basic law adopted in 1992 allows the royal family to select a grandson of Abdul Aziz over the 20-odd surviving brothers and half-brothers of King Fahd, passing over Prince Abdullah, who heads the powerful National Guard.
However, sources close to the royal family previously said the princes have all agreed that the sons of Abdul Aziz should continue to succeed in order of age, before the grandsons are given the chance.
Defense Minister Prince Sultan, who was next in line to the throne after Abdullah, was named crown prince, although rivalry has sometimes been reported between the two men.
The Saud dynasty dates back to the 18th century, when "Lord of the Desert" Mohammad bin Saud joined forces with an austere Islamic reformer, Mohammad bin Abdul Wahhab, and set about propagating by the sword a return to pure Islam.
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