RIYADH, June 16 (Reuters) - Crown Prince Nayef, who died on Saturday, built the formidable security force which crushed an al Qaeda revolt in Saudi Arabia and with it any dissent against his family's century-old grip on the world's leading oil exporter.
To liberals, Nayef, a son of the state's founder, was the forbidding face of a conservative establishment that opposed any real moves toward democracy or greater women's rights, oversaw the fearsome religious police and for years headed an Interior Ministry which imprisoned political activists without charge.
But former diplomats, local journalists and members of the ruling house described him as a more flexible man in private, who survived more than three decades at the centre of a Saudi political system in which dozens of uncles, half-brothers, sons and nephews jostle for influence and fortune.
"Nayef is widely seen as a hardline conservative who at best is lukewarm to King Abdullah's reform initiatives," said a 2009 U.S. diplomatic cable about the prince, who was in his late 70s.
"However, it would be more accurate to describe him as a conservative pragmatist convinced that security and stability are imperative to preserve al-Saud rule and ensure prosperity for Saudi citizens," said the cable, published by WikiLeaks.
Soon after the Sept. 11 attacks on New York in 2001, Nayef infuriated Washington, a close ally and big buyer of its oil, by dismissing the initial reports that Saudi citizens carried out the attacks. It turned out 15 of the 19 hijackers were Saudis.
That incident gave him a reputation in some quarters as anti-Western, but in fact Western diplomats were generally impressed with the way his interior ministry suppressed an al Qaeda bombing campaign inside Saudi Arabia a few years later.
His main concern was battling al Qaeda in the kingdom and in neighbouring Yemen and maintaining a strong barrier against Shi'ite arch-enemy, Iran, according to U.S. embassy assessments.
"Like many of his compatriots, though not King Abdullah, Nayef displays signs of personal prejudice against the Shi'ites, and has taken an increasingly hard line in dealing with Shi'ite unrest throughout the kingdom," said the WikiLeaks cable.
"Some Shi'ite activists see Nayef as the source of most sectarian discrimination," it added.
Nayef was regarded as closer than many of his brothers to the hardline Wahhabi religious establishment whose support had been vital to his father's establishment of the state in the early 20th century. As a result, he enjoyed particular favour from the clergy who provide legitimacy to the royal house.
Nayef's elevation to crown prince, next in line to the throne, after the death of his brother Sultan last year had alarmed moderates and liberals who feared that if he succeeded as king he would stop reforms his brother Abdullah has started.
Like the rest of his family, personal details of the prince's life were rarely confirmed officially, or left vague.
Nayef was born in around 1933 in Taif, the mountain town where the royal court would annually retreat to each year from the stifling summer heat of the desert capital Riyadh and the Red Sea port of Jeddah, the kingdom's second city.
Saudi Arabia had only a year earlier come into being as a state. Nayef's father King Abdulaziz Ibn Saud, over the course of the preceding 30 years of warfare and diplomacy, had united the Bedouin tribes behind his vision of a pure Islamic state. He conquered much of the Arabian peninsula, securing his family's control over Islam's holiest sites at Mecca and Medina.
Growing up in the royal court of the 1930s and 1940s, Nayef is of the last generation of Saudi leaders who knew the austere desert kingdom before the first flush of oil wealth changed it beyond all recognition and let royal relatives live spendthrift lives abroad in the luxury stores and fleshpots of the West.
A son of Ibn Saud by his favourite wife Hassa bint Ahmed al-Sudairi, Nayef was one of seven of her sons who were groomed young for high office and formed their own power bloc within an extended family that included nearly 40 other half-brothers.
Known as the "Sudairi seven", Hassa's sons also included Fahd, who was later king, the late Prince Sultan, Prince Salman, the current defence minister and likely successor as crown prince, and Prince Ahmed, who was deputy interior minister.
Nayef's own son, Prince Mohammed bin Nayef, a well regarded deputy interior minister in the current administration, headed Saudi efforts to root al Qaeda from the kingdom.
Named governor of Riyadh aged only 20, Nayef impressed his father and went on to become interior minister in 1975 where he was soon known as an ally of the Wahhabi clerics who had run the palace school of his childhood.
It was this ministerial role that came to define Nayef by giving him responsibility for protecting the kingdom from internal threats - most frequently from Islamist militants.
"Given his paramount concern with maintaining stability, Nayef's instincts tend towards concessions to religious demands, especially on cultural-social issues," said the leaked U.S. appraisal of him in 2009. "This is sometimes misinterpreted as opposition to reform, but more likely stems from a desire to balance competing social forces."
As the man to whom regional governors answered, Nayef personally handled the petitions of individual Saudi citizens on a daily basis, cultivating a network of supporters across a kingdom where tribal and regional ties still matter.
Despite his fierce reputation atop the internal security forces, Nayef was said by princes to be among the kinder members of the al-Saud dynasty, treating nephews and nieces of the younger generation with more consideration than his peers.
That avuncular side to his character contrasted with the image he sometimes showed to foreign diplomats, who described him as prickly and, in the U.S. appraisal, stiff, slow and shy, despite occasional flashes of "impish" humour.
The domestic intelligence service, the Mabahith which is under Interior Ministry command, has over the years targeted Islamists, liberals and Shi'ites who sought to organise protests or petition the king on democratic reform.
A prominent Saudi rights group, the Saudi Civil and Political Rights Association, in January issued a statement decrying Nayef for failing to investigate allegations of human rights abuses by the ministry.
He had been ill for some time and died in a Swiss hospital. He will buried in the holy city of Mecca on Sunday. (Reporting By Angus McDowall; Editing by Samia Nakhoul and Alastair Macdonald)