RIYADH, Saudi Arabia -- King Abdullah quickly assumed the Saudi throne yesterday after the death of his long-ailing half brother, giving a smooth transition to the leadership of this key US ally and oil giant already grappling with extremists and debating the need for reform.
After a decade as de facto ruler and the prime mover of recent reforms, the popular 81-year-old Abdullah is expected to seek to consolidate his power by bringing more allies into government and perhaps open the door to younger, more modern princes to play a role.
Some people expect him to face behind-the-scenes competition from a clique of half brothers who hold their own powerful posts and have close ties with Saudi Arabia's conservative Muslim clerics, although the royal family's swift backing of the new king hinted at some consensus.
Fahd, the country's absolute monarch from 1982 until he was debilitated by a 1995 stroke, died yesterday at 84 after nearly two months in a Riyadh hospital.
The mechanism of succession moved quickly along tracks laid down long ago: Abdullah stepped in as king, while Fahd's brother Prince Sultan, the 77-year-old defense minister, became crown prince and next in line to the throne.
Abdullah has been the main force behind unprecedented reforms and a heavy crackdown on Al Qaeda-linked militants following a series of terror attacks in May 2003.
Now armed with the power of the throne after years in the more tenuous position of de facto ruler, Abdullah is likely to move to advance supporters into key positions and push forward on the reform and antiterror tracks.
But he must tread carefully: Prince Sultan and others in the close-knit circle of Fahd's full brothers known as the ''Sudairi Seven" hold key security posts and are seen as resistant to swift change.
Few expect Abdullah and his brothers -- like Fahd, the sons of Abdul-Aziz bin Saud, the Bedouin chief who welded the kingdom together under his name in 1932 -- to hold the throne as long as the 22 years that Fahd held it. In the next generation of numerous grandsons, there is no clear line of succession beyond Sultan.
As the family installed Abdullah, Saudis prepared to bury their longest-ruling monarch today with a mix of the austerity dictated by their puritanical Wahhabi version of Islam and the grandiosity befitting a kingdom whose oil riches fueled investment across the Muslim world.
By yesterday, hotels in Riyadh were packed as Saudis flocked to the capital to express their condolences to the royal family and congratulate the new king.
Fahd was to be buried in an unmarked grave at a cemetery alongside previous kings and commoners -- the tradition in Wahhabism, which frowns on the visiting of graves of family or revered figures.
The capital's streets remained busy, and many Saudis said they had prepared themselves for Fahd's death during his long illness. ''We will all pray for Fahd, who was a father figure to us all," said Ibrahim al-Qahtani, who was shopping at a Riyadh mall with his children.
Before becoming de factor ruler, Abdullah had been less inclined than Fahd to see the kingdom intwined in the decades-old alliance with the United States, but he has preserved close ties with Washington.
Abdullah, who has no full brothers among the dozens of children thought to have been fathered by the kingdom's founder, will have to rely on half brothers for support if he is challenged by Fahd's ''Sudairi Seven" clan.
Sultan, the new crown prince and still in charge of the Defense Ministry, is one of the surviving brothers in that clan, which gets its name from their mother. So is Interior Minister Prince Nayef, head of the internal security forces, and Prince Salman, the powerful governor of Riyadh.
Abdullah, who had a different mother, heads the National Guard.
It once was a largely ceremonial unit, but he has built it into a modern 75,000-strong force as a counterweight to the army.
The Sudairi Seven, with close ties to the kingdom's conservative Islamic clerics, have been criticized by some as too slow to crack down on militant groups and to introduce political reforms.
Fahd helped the United States fund Islamic mujahedeen fighters battling the Soviet occupation of Afghanistan.
He tried to bolster his Islamic credentials, taking the title ''Custodian of the Two Holy Shrines" -- Mecca and Medina, Islam's two holiest cities, in western Saudi Arabia.