An Al Qaeda cell believed by the FBI to have helped recruit hijackers for the September 11 attacks on America has been smashed in Usama bin Laden's home region in Saudi Arabia, it emerged last week.

The cell, discovered by investigators from the Saudi interior ministry, is thought to have contained 20 men, all of whom have been detained.

Diplomatic sources said several dozen extremist prayer leaders who urged their young followers to wage jihad (holy war) had also been identified.

Western diplomats believe the crackdown may have averted attacks within the kingdom and prevented volunteers from being dispatched to commit further atrocities in the West.

"There was an Al Qaeda network in the west of the country and the Saudis have broken it up. They have all been arrested," a Western diplomatic source confirmed.

"Members of the network were involved in fund-raising and were in contact with bin Laden in Afghanistan," the source said. "They also recruited some of the hijackers — at least two."

The cell was discovered in bin Laden's Saudi heartland, an area bordering the Red Sea. Of 15 Saudi hijackers, 13 came from this region, which stretches south from Jeddah through the Asir mountains to the Yemen border.

Most were from affluent backgrounds, including Wail and Waleed al-Shehri, two brothers who lived near Abha. They were the sons of a wealthy former car dealer.

As the first British newspaper permitted to visit western Saudi Arabia since September 11, The Sunday Times obtained insights last week into both the background of the hijackers and the sense of crisis their activities have triggered.

It was here that interior ministry investigators focused their inquiries after September 11, assisted by 12 FBI agents who traveled to Saudi Arabia.

"Some of the hijackers were recruited in Saudi Arabia," said the Western diplomat. "They generally seem to be recruited through their association with mosques or preachers who advocate jihad against the West. About 200 imams have been identified who have a hardline view, even for Saudi Arabia."

In Jeddah, the largest city in the west of the country, influential figures described how many young people had been inspired by bin Laden's call to jihad in Soviet-occupied Afghanistan during the 1980s.

"Usama Bin Laden was a hero to everybody," said a prominent journalist in the city. "They called him the sheikh of the mujahedeen."

Many of bin Laden's supporters were middle-class high school dropouts suffering from a slump in economic prospects that made them willing recruits to his cause. A large number of Saudis remain reluctant to accept the involvement of their countrymen in terrorist attacks. Others acknowledge it and believe the country has entered a period of introspection.

"If you have a large family and two of your sons turn out to be the worst criminals in the neighborhood, you have to ask yourself why," said one of Saudi Arabia's most successful businessmen. American critics claim that Saudi minds are filled with anti-Western poison by the imams. Saudis angrily reject this as a bigoted analysis.

"When they talk in the Western press about the textbooks that breed terrorists, why 15 terrorists and not 200,000 terrorists?" asked Prince Turki al-Faisal, the country's former head of intelligence.

Recent history may provide clues to the motivation of the Saudi hijackers. While Jeddah and the capital, Riyadh, are wealthy cities where Cadillacs and Buicks cruise palm-lined streets, impoverished Asir province remains deeply conservative.

Identity cards introduced in recent weeks are being vehemently opposed because they show women's uncovered faces. Its imams are heavily influenced by Wahhabism — adherence to early doctrines and practices of Islam. It is not uncommon for preachers to call for the deaths of non-believers who oppress Muslims, for their "wives to become widows and their children orphans."

When the Soviet Union invaded Afghanistan in 1979, the imams found a particularly receptive audience for their calls to jihad. Thousands of men went to fight in Afghanistan. They returned after a decade feeling neglected, traumatized and disillusioned.

By 1996 bin Laden was back in Afghanistan and the imams had a new enemy in their sights: American soldiers on Saudi soil. A steady stream of men left to join his struggle.

Many Saudis see political reform as essential to prevent groups such as Al Qaeda from attracting support. In the past two years King Fahd has been in poor health. Crown Prince Abdullah, who has taken over the bulk of the duties of head of state, has been more conciliatory towards the reformists.

Many dissenters who had called for democratic reforms in the mid-1990s were released from jail before September 11. They now argue that change should come under the guidance of the royal family.

"September 11 shocked society and it shocked the officials as well," said Dr Mohsen al-Awajy, a partner in a law firm who was detained for four years.

"We now believe these things should be introduced on a gradual timetable." Dr Abdulaziz Alsebail, professor of Arab literature at King Saud University, said the government had already instituted a shura (consultative council) amid debate over whether it should be elected.

There is acceptance, too, that the education system needs to be reviewed. One Saudi familiar with the curriculum said he was shamed by its "ugly" messages about non-believers.

The reformists realize, however, that most of the population appreciates the stability of the al-Saud regime and has little interest in many of the intellectuals' demands.

"This is a deeply conservative society and it's ironic that the royal family is among its more progressive elements," said one Western political analyst based in Riyadh.

However slow the rate of reform, senior Saudis believe that Bin Laden would struggle to rally large numbers of recruits for any resumption of jihad. Not only does he lack a compliant foreign country that he can use as a base, but the radical elements who have acted as his recruiters at home are facing an unprecedented crackdown.