RIYADH, Saudi Arabia — Long-bearded and short-robed, the men of the \o7 matawain \f7 prowl the shopping centers, restaurants and public parks of Saudi Arabia in search of sin.

At the modern Akariah mall, they chastise and wave camel whips at a black-cloaked Saudi woman whose face is exposed. Across town, they shave the head of a Filipino chauffeur because his hair is too long. Outside the Saudi capital, they insist on the arrest of three Australian nurses for allegedly drinking alcohol, holding them for four days in a crowded prison crawling with rats.

Such is the work of the \o7 matawain, \f7 or "religious police," the guardians of public morality in Saudi Arabia. They are the powerful, dreaded enforcers of religious law and social custom based on a puritanical form of Islam that is observed here.

Officially known as the Committee for the Commendation of Virtue and Prevention of Vice, they are the most visible symbol of Saudi Arabia's fundamentalist religious foundation--and the cultural icon that outsiders find most jarring to watch and most difficult to understand.

"The \o7 matawain \f7 . . . serve as a safeguard that is sure to prevent deterioration and protect society from corruption," said Abdulaziz ibn Abdul Rahman Said, the recently appointed director of the virtue and vice committee.

"We firmly believe that ours is the true religion and therefore we must always endeavor to uphold its pillars."

For the \o7 matawain\f7 , an institution that traces its roots to the days of the caliphs and is a cornerstone in a Koran- based legal system, these are complex times.

First they had to cope with the presence of half a million American and European non-Muslim troops sent to Saudi Arabia to fight the Persian Gulf War.

Then, they were frustrated by orders not to harass American women soldiers who violated local customs by driving cars and exposing their elbows. Their frustration was often vented on Saudis.

And now, questions are being raised in high places about the purportedly abusive practices of some of the \o7 matawain\f7 . Their new leader, a highly regarded theologian appointed late last year by King Fahd, is speaking out about adjusting a few things.

Said suggested shaping the organization into a more professional morals squad committed to teaching by example, not by harassment. Many of the more heavy-handed tactics, it is argued, are the work of vigilante, self-proclaimed \o7 matawain \f7 that officials cannot control.