BEIRUT, Lebanon--Syrian jet fighters and U.S.-made Israeli planes dueled south of Beirut yesterday in the biggest air battle over Lebanon in three months.

Syria said it sent fighters to intercept the Israeli warplanes after the Israelis attacked civilian camps--presumably Palestinian--in the Damour area ten miles south of Beirut.

The Israeli military command said its jets, including the F-15, America's most sophisticated fighter, were on a reconnaissance mission over Palestinian guerrilla bases.

Both sides said four Syrian MiGs were downed. Syrians said it hit two Israeli jets, but the Israelis said all their planes made it safely back to base.

Lebanese government sources said two of the Syrian planes crashed in flames near the airport, and their pilots parachuted to safety. The other two reportedly went down farther into the hills.

A Syrian military communique issued in Damascus said two Israeli jets were "hit" as well but did not say specifically where they had crashed.

The Syrians, whose 22,000 troops police a civil-war armistice in Lebanon, have pledged to defend Lebanese territory against Israeli air attacks. Israeli jets frequently fly over Beirut and southern Lebanon on surveillance missions, or to attack Palestinian positions.

The U.S. State Department had no comment yesterday on whether Israel's use of F-15s over Lebanon violates U.S. restrictions limiting the aircraft to self-defense missions.

The Israelis say their Lebanese operations are pre-emptive missions to defend against Palestinian attacks.