Walid Jumblatt, the leader of Lebanon's Moslem Druze community, was slightly injured today when a bomb exploded nine feet from the car that he was driving in downtown Beirut. It killed four persons and wounded at least 15 others.

In an obvious attempt to head off another round in the already escalating sectarian violence between Druze and Christians, Jumblatt issued an appeal a few hours after the assassination attempt urging calm among his Druze followers.

"This incident should not affect efforts to bring peace to Lebanon," Jumblatt, 33, said in a statement read over the nation's state-run radio and television. "I am in good condition, and such things are expected to happen."

No group claimed responsibility for the attack. The Christian Lebanese Forces militia, whose members have been fighting with Druze militiamen in the Chouf Mountains southeast of Beirut, denounced the bombing and said that it was not involved.

Less than an hour after the blast, Lebanese security sources reported new violence in the Chouf area, United Press International said. Several shells fell near Christian positions in the district, and three Druze were kidnaped.

[UPI also reported that the bomb that injured Jumblatt exploded two blocks from a building where U.S. envoy Morris Draper was holding talks with Lebanese officials. Security personnel whisked away Draper immediately after the explosion.]

Jumblatt was pulled from the back window of his badly damaged Mercedes and rushed to the American Hospital, where he was treated for light chest and scalp wounds. His wife Gervette, who was with him, was reported suffering from shock but otherwise uninjured.

Jumblatt later appeared on television wearing a small bandage on the left side of his scalp but otherwise appeared to be in good condition. He called the attack a "minor incident" aimed at provoking sectarian tension.

In remarks to reporters at his headquarters, Jumblatt refused to speculate on who might have been behind the assassination attempt, saying, "This is not the time to accuse. The main thing is to secure Lebanon."

Violence against political leaders in Lebanon has increased since the 1975-1976 civil war. A bomb in Beirut killed Lebanon's president-elect, Bashir Gemayel, in September.

The incident today highlighted the mounting tensions that result from the fighting between Druze and Christians in the Chouf and threaten the fragile peace in the capital area. Since mid-October, more than 100 persons have been killed and 200 others wounded in sporadic clashes between Druze and Christian militamen in the Chouf. Scores from both communities have been kidnaped, and their fate remains unknown.

There were immediately fears that the attempt on Jumblatt's life might spark a repeat of the Druze massacre of Christians in the Chouf following the assassination of his father, Kamal, in March, 1977. Several hundred Christians died in that bloodletting, although there was no evidence that they were involved in Kamal's assassination, and later the Syrians were widely suspected of being responsible for it.

The Israeli Army has moved reinforcements into the Chouf area and patrolled the roads to keep the two militia forces from going at each other full tilt. But this has not prevented numerous incidents from occurring, such as the kidnaping of 21 Druze and Christians in the past few days.

The Druze, who belong to an offshoot of the Shiite branch of Islam, number about 200,000 in Lebanon. In addition to leading the Druze community, Jumblatt heads a loose coalition of leftist Moslem groups called the National Movement.

Today's attempt on Jumblatt's life took place in mid-afternoon as he was emerging in his car from an underground garage on Michel Chiha street, the extension of West Beirut's main Hamra thoroughfare, after he had lunched at a friend's home.

The powerful bomb apparently was hidden in a car stationed near the entrance and set off by remote control as Jumblatt's Mercedes reached the street. The blast set afire at least six cars and seriously damaged half a dozen others parked or passing in the street.

Jumblatt's vehicle did not catch fire, and this may have saved his life, because the damage made it impossible for him and his wife to escape through the front doors.

Among those who died was Jumblatt's personal bodyguard, Jamal Saab, who was sitting in the back seat of the Mercedes. Jumblatt was driving, and his wife was sitting next to him in the front seat. A Lebanese policeman also was killed.

Jumblatt's Druze followers gave him a triumphant welcome at his headquarters and home after he returned from the hospital less than two hours after the bombing.

He had been meeting in the morning with President Amin Gemayel, former president Camille Chamoun and Lebanese Forces officials to discuss ways to resolve the Druze-Christian confrontation in the Chouf. Such meetings previously have failed to reach any concrete decisions to reduce tensions, and none was announced today.