Kamal Jumblatt, the leader of Lebanon's leftist Moslems, was assassinated by unknown gunmen today, raising immediate fears of renewed Christian-Moslem bloodshed.

A police spokesman said Jumblatt and two of his bodyguards died instantly when their car was riddled by machinegun fire near the town of Banglin, in the mountains, 21 miles southeast of Beirut.

The assassins' getaway car was later found abandoned in a nearby village. Police said they found three Soviet-made Kalashnikov automatic rifles and a pistol in it.

There was no immediate indication who the killers were or what caused they espoused. The Chouf district where the attack took place is home base to maronite Christians and to Moslem Druze.

Troops of the Arab peacekeeping force were immediately put on full alert and put up roadblocks around the capital. Shops in Beirut and other districts began to close down as the news spread.

Jumblatt, 59, the overall leader of the Moslem leftist faction in Lebanon, that played a pivotal role in the II- [WORD ILLEGIBLE] civil war, repeatedly blocking moves to bring about a compromise settlement and bitterly opposing intervention by the Syrian forces.

Friends of Jumblatt noted that he had recently been under pressure from Syria, whose troops make up the bulk of the Arab force that is [WORD ILLEGIBLE] the cease-fire in Lebanon. About a week ago three high-ranking Syrian officers reportedly asked Jumblatt to go to Damascus to confer with Syrian President Hafez Assad but Jumblatt refused.

There was no official reaction from Syrian today on the assassination. In Cairo, shaken Palestinian guerrilla leaders whose forces fought alongside Jumblatt's Moslems in Lebanon, called for revenge.

Leanese Premier Selim Hoss went on television tonight to urge restraint by Lebanese. He denounced the murder as a move intended to plunge the country back into conflict.

Walid Jumblatt, the only son of Kamal Jumblatt, pleaded on television, "Let this day be one of the national unity for which Kamal Jumblatt died a martyr."

In Washington, the State Department deplored the slaying and extended its sympathy to Jumblatt's family and friends.

Jumblatt, an ascetic milliona-landlord, was the leader of Lebanon's Progressive Socialist Party and the tribal chief of the country's Druze. He was the overall leader of the alliance of leftist Lebanese Moslems and Palestinian guerrillas two battled in the 19-month civil war against rightist Maronite Christians.

The news of his assassination was followed in Beirut by an eruption of gunfire and explosions both in Moslem and Christian sectors. But there were no immediate reports of renewed Christian-Moslem fighting.

A government statement broadcast by Beirut Radio said all necessary measures were being taken "to prevent repercussions which would only benefit those harboring evil intentions against Lebanon."

Jumblatt was killed on a twisting mountain road a few miles from Moukhtara, his ancestral home.

Three gunmen in an Iraqi-registered sports car swerved in front of Junblatt's car and shot him through the head and chest before escaping, according to local journalist.

Across a deep mountain valley, in full view of the spot where Jumblatt died, is the native village of one of his bitterest political foes, right-wing former President Camille Chamoun. The men were life-long rivals in the wooded mountain district known as the Chouf, where Jumblatt has his main power base among the Druze community.

Jumblatt's death underlines the violence of the region. In Lebanon and neighboring Syria there have been four unsuccessful attempts on the lives of political leaders in the past year.

Three of the recent assassination bids were against Raymond Edde, a Christian moderate who, like Jumblatt, was an outspoken critic of the Syrian role in Lebanon.

The other attempt was on Syrian Foreign Minister ABdel Halim Khaddam late last year.

Jumblatt's body was brought to Moukhtara and his son said a simple funeral would be held there Thursday.

While the son will inherit his father's family authority and Jumblatt associate Tawfiq Sultan was desginated to take over Jumblatt's army, there is little indication that anyone has the stature to replace the slain leader as overall head of Lebanon's leftist faction.