The sheik twisted nervously in his chair. An ambitious but obscure holy man in Beirut's teeming Shiite Moslem slums, he has suddenly found unwanted recognition, accused by Lebanese investigators of playing a major role in the suicide bomb attacks on U.S. and French peace-keeping troops last Sunday.

In his shabby seventh-floor walkup in the slums, Sheik Mohammed Hussein Fadlallah was being tended to today by followers, some of whom had Kalashnikov assault rifles in ready position.

Fadlallah, in an interview with The Washington Post, said he was mystified by the charges. He said he was a peaceful man, harbored no grudges against either the U.S. Marines or the French and has always preached against violence.

Asked why, then, there were so many guns around him, he laughed for the only time. "This is for people who don't understand my concept of peace."

Investigators who would not be identified said Fadlallah provided the two suicide drivers for the bomb-laden trucks that attacked the military positions. Investigators say he went to the Shiite neighborhood near the Marine compound to give final blessings to the drivers.

Lebanese authorities said they had passed on to the Marines and FBI the names of 11 persons they suspect of having been involved with Fadlallah in carrying out the operation.

It is widely asserted here by Lebanese and foreign diplomats that the operation was masterminded by Syria with the aid of Iranian agents. They doubt that Fadlallah and his followers have the skill or the resources to handle such an operation alone.

It is considered unlikely that Lebanese authorities will move soon to arrest Fadlallah. The Army has avoided going into the Shiite slums for the last two months for political reasons. To do so now would be likely to spark fierce clashes with the thousands of armed young men who roam freely there and could ruin whatever slender chances exist for peace accords among the government and opposition factions meeting in Geneva next week.

On the other hand, Fadlallah has scant resources to counter the charges, made by investigators with a poor track record for solving the numerous assassinations and bombings here over the years.

Fadlallah called the allegations a frameup by Christian Phalangist militiamen in league with Lebanese Army intelligence. He said they were concerned about his growing power and were trying to cut him down.

Fadlallah's movement is obscure. Investigators attempting to track down his photograph early this week did not know his name. The mainstrean Shiite group Amal has far more followers and gunmen than Fadlallah, according to all accounts here, and even other splinter Shiite groups in Lebanon are larger, according to local journalists familiar with the organizations.

Although investigators depict Fadlallah as leader of an extremist faction with links to a Moslem fundamentalist group in Iran, his politics are a matter of confusion for longtime observers. Fadlallah acknowledges ties in Iran, but others here said his main backers in Lebanon have been among landed gentry and political barons in southern Lebanon that Amal fought.

Fadlallah, 49, said he was born in Iraq, the son of Lebanese, came to Lebanon as a teen-ager, studied religion in the Shiite holy city of Najaf in Iraq and become a spiritual teacher in southern Lebanon.

He has a mosque in Beirut's southern suburbs, an orphanage and a school for sheiks, he said. His followers consider him the "most trustful judge" in all matters, he said, especially in religious concerns.

Fadlallah said he welcomed the arrival of the Marines last year because they got the Israelis out of Beirut's airport. But he would not say whether he thought they should stay or leave.

At any rate, he said, he was at his apartment on Sunday morning, nowhere near the airport. He said he does not believe in suicide missions and rejects the belief among some Moslem fundamentalists that those who carry out such acts for religious reasons immediately ascend to paradise.

"Paradise is not within our hands to give to people," Fadlallah said as he sat in a little room of his dank tenement. "Paradise is in the hands of God."