The sheik who was the target of a car-bomb attack by a group with ties to the Central Intelligence Agency last March has repeatedly been accused of plotting the bombing of the U.S. Marine headquarters in Beirut in October 1983. But there has never been any conclusive proof that he really participated in planning and executing the terrorist operation.

Some reports suggest he may have provided the religious justification for the action, even the final blessings to the suicide driver of the truck laden with explosives that drove into the Marine compound. But even these reports are still the subject of dispute among Middle East intelligence analysts.

Much of the information originally implicating the sheik in that bombing came originally from Christian-run intelligence services that had their own reasons for wanting to implicate and assassinate a man who had become their bete noire.

Publicity in America about his alleged role in the attack on U.S. Marines, which left 241 American servicemen dead, however, has helped transform Mohammed Hussein Fadlallah from a little-known cleric in a southern suburb of Beirut into a major spiritual leader of Shiite Moslems whose books are now read across the Arab world.

Had the March assassination attempt succeeded, there is little doubt it would have caused a major backlash, with Shiite militants everywhere seeking to take revenge against U.S. targets in Lebanon and other Arab countries.

The whole episode raises questions not only about the use of foreign nationals to carry out antiterrorist activities, but also about the sources the United States relies on for information about terrorist groups, particularly in Lebanon.

Ironically, the influential sheik was recently asked to become an intermediary in helping the United States gain the release of the kidnaped Americans being held in Lebanon by an unknown Shiite militant group. It is asking for the release of 17 Shiite extremists from prison in Kuwait in exchange for the Americans.

Almost from the day of the Oct. 23, 1983, bombing, the United States and other western embassies in Beirut began receiving reports that the militant Shiite group Hezbollah, the Party of God, and its alleged leader, Fadlallah, were behind the operation.

"Washington wanted a name and his started showing up in reports," remarked a U.S. diplomat formerly stationed in Beirut. "There was the devil."

The original sources for all these accusations, however, were the Lebanese army's Christian-run intelligence branch, known as the G-2, and the right-wing Christian Lebanese Forces militia's own intelligence service. The two have had close ties for years and regularly exchange information.

For the Christian militia and its allies in the army's G-2, Fadlallah was long the symbol of a burgeoning, militant Shiism that sought the creation of an Islamic republic in Lebanon -- which the Christians saw as a threat to the existence of the Christian population in the country. Even before the bombing of the Marine headquarters, these Christian-led intelligence agencies had pointed to Fadlallah as a leading pro-Iranian Shiite cleric stirring up his community against the Christians.

The U.S. Embassy, which conducted its own study of Shiite leaders in southern Beirut prior to October 1983, then found little evidence to support this alarmist portrayal of the sheik. Instead, it discovered that Shiites generally regarded him as part of the "straight establishment," which, as a member of the Higher Islamic Council, he was.

But Fadlallah's name had come up before the Marine compound bombing in connection with at least one kidnaping operation. It was said that Fadlallah had advance knowledge of the incident.

Both U.S. and Israeli intelligence singled out Fadlallah as a principal organizer of the Marine barracks bombing and other anti-Western terrorism. But it was no secret to reporters based in Beirut at the time that both intelligence services were getting much of their information from either the G-2 or Christian militia intelligence.

"They shared a lot of information," said a knowledgeable U.S. military source with long experience in Lebanon.

According to the U.S. diplomat who formerly served in Beirut, "The stuff on the Marine barracks was very iffy and all G-2."

Later, other U.S. intelligence reports, said to be independent of the G-2 or the Christian militia intelligence service, reportedly also linked Fadlallah to the 1983 bombing. The reports said he had participated in a meeting in Damascus three days before with suspected terrorist operatives. His role at those meetings remains obscure, however. The source of these later independent U.S. intelligence reports is unclear.

The United States used to gather some of its most valuable information about Moslem activities in West Beirut from Palestinians, sometimes from members of the Palestine Liberation Organization itself. But with the ouster of the PLO from Beirut in late August 1982, these sources dried up, creating an intelligence gap for the CIA in Lebanon and a growing dependency for information on the G-2 and other Christian sources.

Sheik Fadlallah's role in organizing, or blessing, anti-Western terrorist activities in Lebanon remains subject to much debate and little precise information to this day. In appearance and word, the sheik comes across as an erudite scholar, which he undisputably is, rather than a terrorist operator.

Furthermore, he has openly spoken out at times against both suicide bombings and hijackings, which he called "un-Islamic," and several times urged the Shiites living in the southern Beirut suburbs not to seek revenge on westerners.

In November 1983, during a particularly tense moment immediately after a French air raid on militant Shiite camps in eastern Lebanon, the sheik publicly called on his followers not to seek revenge.

Perhaps the closest direct link established between Fadlallah and the Marine compound bombing was his relationship with Hussein Musawi, a follower of the sheik who led the extremist group Islamic Amal and helped set up the militant Hezbollah, according to a Washington Post investigation of the bombing incident early last year.

However, a Beirut-based American reporter for the Sunday Times of London, Robin Wright, who has just finished a book on Shiite extremism, said she had been unable to find evidence of a direct connection between Fadlallah and any of the bombings, or with Hezbollah.

"Every source I spoke to, including some of the most militant Shiites, claimed that he had no direct links to any of the extremist groups," she said in an interview.

Rather, Fadlallah has become a spiritual leader to Shiites in various groups, "like Ayatollah Khomeini."

Lebanese sources said Fadlallah now ranks among the highest religious authorities in contemporary Shiism, an offshoot of the main Sunni school of Islam. This is a sharp contrast to his reputation before the bombing of the Marine barracks in 1983. Then, the sheik was hardly known outside his own squalid quarters in the southern Beirut suburb of Bir Abed.