The Palestine Liberation Organization freed its two Israeli prisoners today, clearing the last obstacle to the scheduled peaceful evacuation of its guerrillas from besieged West Beirut.

The release of the prisoners, who returned to Israel along with the remains of nine Israeli soldiers killed in Lebanon, set the stage for the 14-day PLO evacuation negotiated by U.S. special envoy Philip C. Habib to begin Saturday.

The evacuation plan began to take shape early Saturday morning when the first contingent of 350 French legionnaires disembarked at the Beirut port, The Associated Press reported. The French unit, members of the Foreign Legion's 2nd Foreign Parachute Regiment, is the vanguard of a multinational force that will include U.S. Marines.

The plan for the French arrival went awry at the beginning. The Lebanese Army, which was to have taken over control of the port area from the Israelis and Palestinians, was nowhere to be seen and both opposing forces still held their positions. Angry words were heard among the French, Israelis and a Lebanese officer who arrived after the French ship came to port.

It was unclear why the Lebanese had not taken control of the port area, but the French troops marched off their ship and moved out into the areas controlled by the Israelis.

The prisoners, Air Force Capt. Aharon Ahiaz and Army Pvt. Ron Harush, were turned over to the International Red Cross this afternoon in the heavily bombed Fakhani district of the Lebanese capital. They were immediately driven across the Green Line dividing West Beirut from the Israeli-held eastern sector by way of the port of Beirut crossing and turned over to Israeli military authorities.

Shortly afterward, bodies of the nine men, five killed in this summer's invasion of Lebanon and four others killed during a 1978 Israeli invasion, were placed in wooden caskets on a Red Cross truck and driven along the same route into East Beirut. There they also were turned over to the Israelis.

The two former prisoners returned to Israel late this afternoon, landing at an air base in north Tel Aviv where they were met by family members and senior military officials.

But even as the evacuation was set to begin, Israeli military officials tonight accused PLO guerrillas of breaking the cease-fire along the eastern front in Lebanon. They said PLO rocket fire killed a Lebanese tractor driver.

Col. Abu Zaim, head of PLO intelligence, told a press conference announcing the prisoners' release, "We have preserved the life of this pilot and his colleague. You see we are not terrorists as Mr. Begin likes to say."

"We plan on leaving now, taking our arms and weapons with us and with our heads held high," he said, alluding to the peaceful evacuation of PLO fighters and their Syrian allies that is to begin Saturday.

Ahiaz, who had been shot down while piloting a Skyhawk fighter-bomber on June 6, the first day of the Israeli invasion of Lebanon, told foreign reporters here who crowded around him moments before he was rushed off that he felt "very happy" to be going home.

"I was treated well," said the pilot, who was dressed in slacks and a checkered cotton shirt. "But I don't want to make any political statements."

"A war is always a tragic situation," he said as his co-captive, captured from a position near the suburb of Burj al Barajinah two nights ago, stood by silently. "I hope there will be no more war now."

The freeing of Ahiaz and Harush and the return of the nine bodies had been Israel's last condition to its acceptance of Habib's plan to end Israel's 10-week siege of West Beirut.

The Israeli Cabinet yesterday approved Habib's painstakingly negotiated accord but said that until the prisoners and bodies were back in Israeli hands the implementation could not begin. This afternoon, after the prisoners and bodies had been transferred into East Beirut, Lebanese Prime Minister Shafiq Wazzan said that he hoped that there would be no further delays.

"Now everything is ready for implementation," Wazzan said. "I hope no emergency will occur to delay this implementation."

According to the evacuation plan, after the French force takes control of the harbor, the first group of PLO fighters, reported to be 400 men who will be going eventually to Iraq and Jordan, will be brought to the port from an assembly point at the municipal stadium in West Beirut. They will board ships there and be escorted to Cyprus by the French Navy vessels. In Cyprus, they will board chartered Jordanian and Iraqi airline jets to fly to their final destinations.

A total of 2,000 to 2,500 PLO fighters are scheduled to depart during the next three days, after which the bulk of the multinational force that is to oversee the withdrawal is due to arrive. This force will be made up of U.S. Marines, more French paratroopers, and a unit of Italian troops who are already steaming toward Lebanon by ship.

Once the full force of 2,000 foreign soldiers has arrived, they will be deployed along with soldiers from Lebanon's Army in positions around West Beirut.

After this deployment is completed, the main PLO force will begin pulling out, leaving its positions to gather in West Beirut for what will be a seven-day transfer by road to Damascus.

The Associated Press reported the following from Tel Aviv:

Ahiaz was greeted at the air base by his wife and son with a bunch of flowers. Harush was welcomed by his mother.

Ahiaz, holding the boy in his arms and smoking a cigarette, told reporters at the airport, "I'm happy that everyone shares my joy."

Harush said he had shared his last two days with Ahiaz in the Beirut apartment where the guerrillas had held the pilot since his capture.

The two captives were handed over to the Israelis at 5:15 p.m. (11:15 a.m. EDT). Ten minutes later, a Red Cross truck arrived with the coffins of the nine soldiers whose remains were also turned over by the PLO.

Israeli radio described the scene as a mixture of rejoicing at the release of the prisoners and sorrow for the dead.

Military chaplains wearing rubber gloves opened the coffins and hastily inspected the bodies as dusk on the Jewish Sabbath approached. According to Jewish tradition, contact with the dead should be avoided during the Sabbath.

"We will bury you in our holy earth," intoned the chief military chaplain, Maj. Gen. Gad Navon.