U.N. peacekeeping forces in south Lebanon yesterday reported at least 10 persons killed and 15 wounded in a serious escalation of fighting between Israeli-backed rightists and Palestinian and Lebanese leftist guerrillas.

A spokesman for the U.N. force quoted refugees for the casualty figures. They said most of the deaths resulted from a three-hour artillery exchange Tuesday near the village of Kleya. The region, near the strategic Litani River, is just outside the area under U.N. control.

In a related development, official sources yesterday said that Lebanese President Elias Sarkis has won Syrian consent to use regrouped Lebanese Army units to patrol guerrilla-controlled area in southern Lebanon.

The sources said Sarkis was also given use of Syrian troops to help his army establish a buffer zone between Palestinian guerrillas and U.N. peacekeeping forces in the Israeli-occupied areas of the south. Since the 1975-76 civil war, 30,000-man Arab peacekeeping force, largely made up of Syrians has controlled most of the country, but not the south.

In Latakia, Syria, Syrian President Hafez Assad said he agreed with Sarkis that the Lebanese Army should enter the south. The two leaders ended a two-day meeting yesterday.

In another Middle East development, Israeli U.N. Ambassador Chaim Herzog yesterday called for an all-embracing Arab-Israeli disarmament conference "to break the vicious cycle of arms buildup" in the region. Just hours earlier, Herzog said in a television interview that he did not believe the current U.N. disarmament conference would produce anything. He said Israel would ask the United States for more arms.

Herzog also accused Egyptian Foreign Minister Mohammed Ibrahim Kamel of "attempting to mislead" the conference in a speech Wednesday, when he alleged that Israel cooperated militarily with South Africa.