Palestinian rebels today clashed with forces loyal to guerrilla leader Yasser Arafat in eastern Lebanon in the first violence of the nearly four-week-old mutiny in the ranks of the Palestine Liberation Organization.

Police sources in the Bekaa Valley said eight persons were killed and 17 wounded in the hour-long fighting two miles west of Baalbek between rival factions of Arafat's Fatah organization, which is the mainstream of the PLO federation.

Each side blamed the other for starting what Palestinian officials said was the first major fight among guerrillas in nearly a decade.

High-ranking Palestinian officials belonging to neither faction said here that they were surprised by what they called an "isolated incident" and hoped it would shock the combatants into a rapid solution of their differences.

Only yesterday PLO Chairman Arafat had felt confident enough about the peaceful outcome of the rebellion to have resumed his travels, flying off to visits in Romania, Algeria and India.

His principal lieutenants asserted publicly that the rebellion constituting the gravest internal challenge to his long stewardship had been "contained."

They predicted that Arafat would return to lay down the law to the rebel ringleaders, who steadfastly had refused all proffered compromises.

Units loyal to Abu Musa, leader of the mutiny, chased a small force of pro-Arafat fighters out of the town of Hawsh Bardah, five miles west of the ancient town of Baalbek, Lebanese government sources said, according to United Press International.

The fighting began at 10 a.m. (4 a.m. EDT) and continued through the day, the sources said. The state-run Beirut radio said it had received unconfirmed reports of up to 40 people killed or wounded.

A Lebanese government source said the anti-Arafat dissidents already controlled several villages between Baalbek and the Syrian border, while the Arafat loyalists controlled Baalbek and access to the town from the north.

Abu Jihad, the nom de guerre for Arafat's aide Khalil Wazir, said Saturday's fighting started with an attack on a group of Fatah officials sent to the Bekaa to investigate attempts by the dissidents to control the main road between Baalbek and the Syrian border to the southeast, UPI reported.

Since the mutiny began both sides repeatedly have stressed their abhorrence of resorting to fighting to settle differences, and officials have predicted Arafat was contemplating nothing more rigorous than excommunicating fewer than a dozen rebel officers.

Neutral Palestinians said Arafat's patience in dealing with the crisis would help to reassert his shaky authority over the PLO, which in the past 15 years has become all but synonymous with him.

Lending further support to Arafat was a message from Soviet leader Yuri Andropov that, according to the Palestinian news agency Wafa, "stressed the importance of Palestinian unity under the umbrella of the legitimate leadership of Yasser Arafat."

Earlier in the week, two Damascus-based Soviet diplomats had visited Arafat in the northern Lebanese port of Tripoli on a similar mission.

Key Palestinians, foreign diplomats and Syrian insiders helped piece together the tale of yet another chapter in the PLO's tribulations as the wild card in the Middle East poker hand.

Their story involved grievances among rank-and-file Palestinian fighters--not all of them Fatah members-- neglect and even indifference by the leadership and charges of Libyan and Syrian backing for the rebels' efforts to whittle Arafat's authority, if not supplant him.

Barring more internecine fighting, Arafat's lieutenants say that he stands to emerge from the lingering showdown with renewed grass-roots support for a tough policy aimed at confronting Israel, pressuring conservative prowestern Arab states and maintaining a real measure of independence from Syria.The challenge this month has drawn so much attention partly because the revolt appears to involve Fatah, which accounts for 80 percent of Palestinian guerrilla fighters and is considered Arafat's private power base. To some observers the strangest aspect of the mutiny is that great numbers of sympathizers--if not the active rebels--initially were swept along by what appeared to be an almost childish desire to cause trouble to attract an often distracted Arafat's undivided attention.

"I am not worried, but I am embarrassed," said one Palestinian leader as he expressed fear that the already battered image of Arafat and the PLO in the outside world has been tarnished further by the yet unresolved crisis.

"Arafat needed a shock," he added. "And he will draw the necessary lesson."

The shock was the deeply felt need for reform and cleanup of the PLO, which an autocratic Arafat had come to dominate. Yet he had been forced to govern from afar since the PLO's eviction from Beirut last summer as a result of Israel's invasion of Lebanon.

Most observers agree that if the tide is turning in Arafat's direction, as his advisers suggest, it is due to the perceived danger of splitting Fatah. Even the majority of Arafat's rivals in the seven other member organizations of the PLO are known to fear that such an outcome could only mean domination by one Arab government, or a combination of them.

Over the years Arafat repeatedly has sacrificed ground--and often avoided key decisions--rather than compromise the unity of the PLO.

Despite accusations of weakness, Arafat's key advisers are convinced they have been correct in giving the rebels' enough rope rather than cracking down on them from the start.

"In any other Third World situation, especially in one of the Arab world dictatorships that President Reagan supports, the opposition would have been immediately suppressed and no one would have known about it," said a spokesman for the Marxist Democratic Front for the Liberation of Palestine.

The mutiny broke out May 7 when Musa, the deputy chief of PLO military operations, walked into the headquarters of the Yarmouk Brigade in the Lebanese village of Aita El Foukhar, a few miles south of the Beirut-to-Damascus highway near the Syrian border.

He seized control and prevented the headquarter's commander from reporting the incident. The commander drove to Damascus, less than an hour's trip, where he reported to Abu Jihad. It was past midnight.

Abu Jihad recalled recently that he told the commander to get some sleep. He was convinced the problem could be solved quickly, a delusion he maintained for the better part of two weeks as one delegation of loyalist officers after another failed to convince Musa to return to the fold.

Syrian officers, according to Palestinian insiders, were present and were advising Musa.

In retrospect, Abu Jihad may have been overly optimistic in his initial reckoning. For Musa, according to general consensus, was perhaps the only man who equalled Arafat's reputation and popularity with the troops.

Abu Jihad's overconfidence was based on Arafat's knowledge that a plot had been afoot for months in the Bekaa.

Although no Palestinian officials will say so on the record, in private they insisted that since the winter they have possessed documents implicating Syrian intelligence.

Since the mutiny erupted, Arafat has accused Col. Muammar Qaddafi of involvement, and the Libyan leader has openly backed the rebels and boasted that he provided them with arms and money. In fact, the mutiny reflected unresolved problems bedeviling the PLO since it lost its independent power base in Beirut and became more vulnerable to outside pressures.

Seemingly a hero in defeat who was involved in negotiations with the United States, although via third parties, Arafat last fall chose to trust U.S. diplomacy to help achieve his dream of a West Bank state. Conservative Arab governments encouraged him in that course.

That dream ended April 9 when he failed to persuade Fatah's central committee to approve PLO backing for talks that King Hussein of Jordon hoped to initiate on the future of the Israeli-occupied West Bank and Gaza Strip.

Arafat's intelligence had expected the Bekaa mutiny before the Palestine National Council meeting in Algiers during the winter. Then later officials expected it if Arafat decided to join Hussein in negotiations.

Despite these early warnings, Arafat apparently was surprised when the mutiny broke since he met on April 22 for the first time in many months with Syrian President Hafez Assad to work out a new political understanding after the breakdown of the talks with Jordan.

Many of the rebels' specific complaints referred to Arafat's freewheeling diplomacy during the period of negotiations with Jordan.

Arafat said only 150 Fatah men were involved in the mutiny. Independent officials put the total number of Palestinian rebels at no more than 800.

Abu Jihad said Musa's Fatah contingent of fewer than 100 men had been joined by 600 Libyan soldiers and other groups.

Also involved were followers of pro-Libyan Ahmad Jibril, leader of the Popular Front for the Liberation of Palestine--General Command, and of Abu Nidal, the cashiered Fatah leader who has specialized in killing Israeli officials and moderate Fatah leaders favoring dialogue with Israel.

Even if Fatah personnel constituted a minority of the rebels, their grievances and radical suspicions of any talks were widely shared.

If nothing else, the mutiny appears to have brought home to Arafat the necessity of keeping in touch with the rank and file.

For the past two weeks he has had to barnstorm around garrisons in Lebanon, patiently listening to his men's complaints, sharing their often meager fare and bedding down alongside them.

He was reported to be considering dividing up his central committee and stationing various members in Syria, Lebanon and other countries.

The mutiny has made obvious the unpleasant notion that if he cannot command the respect of his guerrillas, Arafat's larger claim that the PLO is the sole legitimate representative of the Palestinian people will lose crediblity.