A strong Israeli force that landed in southern Lebanon last night was engaged in heavy fighting early today with Palestinian and Lebanese leftist forces, the Palestinian news agency WAFA reported in Beirut.

In Tel Aviv, however, Army spokesman said all the Israeli commands had returned safely by helicopter after destroying an Arab liberation front headquarters at a base near Nabatiyeh, Lebanon, and killing 10 guerrillas.

The Palestinian guerrilla command said the assault force suffered "heavy losses" and three Palestinians were killed or wounded in the attack. It said three civilian houses were destroyed.

A Palestinian dispatch reported battles at Kfour and Zefta, near Nabatiyeh, a guerrilla strongpoint 10 miles from Israel and 35 miles south of Beirut.

The Palestinian command said about 200 Israeli troops were involved and the guerrillas had thrown up a "tight siege," preventing the commandos from withdrawing.

Some Israeli troops landed at Zefta, apparently to prevent reinforcements from reaching the guerrillas at Kfour, the guerrillas said.

"Our forces besieged the enemy troops, and heavy fighting with all kinds of weapons" took place, they added.

Israeli artillery began shelling Kfour at midnight (5 p.m. EST) to cover the withdrawal of the Israeli commandos, the Palestinian report said, while Israeli helicopters and warplanes continued to drop flares over Nabatiyeh and the Mediterranean cities of Tyre and Sidon to the west.

Israeli gunboats were reported shelling Kassemieh, five miles north of Tyre.

An earlier Palestinian dispatch reported that Israeli military units also had moved into some areas of southern Lebanon controlled by Israeli-backed Lebanese Christian militias.