BEIRUT, OCT. 10 -- Israeli warplanes struck just 500 yards from a big parade of Palestinian guerrillas and officials in eastern Lebanon today, Palestinian sources said.

Four warplanes dropped more than 20 bombs on a base of the radical Popular Front for the Liberation of Palestine (PFLP) in the mountainous area of Yanta, five miles from Syria's border in the Bekaa Valley.

"They barely missed the graduation ceremony of more than 300 fighters. There were many PFLP officials there as well," one source said. One guerrilla was wounded in the raid, he said, adding: "Had they scored hits on the gathering, we would have had a massacre on our hands."

In Tel Aviv, a military spokesman said the Israeli raid was against "terrorist bases" near Lake Qaroun, west of Yanta.

Witnesses said the Israeli warplanes destroyed a house used by the PFLP and an ammunition dump. It was the 22nd Israeli raid on Lebanon this year.

In southern Lebanon, Palestinian guerrillas near the port of Sidon were reported to have pulled back from positions they captured east of the town in clashes with the Shiite Moslem Amal militia.

The two guerrilla groups had been engaged in heavy fighting earlier this week.

Mustapha Saad, leader of the Nasserite Popular Liberation Army controlling Sidon, said his militiamen moved into the two villages at noon as a buffer between the Palestinians and Amal.

The renewed clashes had stalled a Syrian-brokered peace pact that was to have taken effect on Oct. 5, to end a three-year "camps war" in which 2,500 people were killed.

The pact provided for the Palestinians to withdraw from areas east of Sidon and Amal to end its siege of camps in Beirut and south Lebanon.

In the Syrian-controlled northern city of Tripoli, a car bomb killed three people, police said. The car exploded at the entrance to a seafront hospital and set four other cars ablaze.