A heavy barrage of rockets fired from Palestinian guerrilla positions in Southern Lebanon killed three persons and wounded 13 others tonight in the Galilee region of northern Israel.

The Israeli Army command said "scores" of Katyusha rockets fell on the Mediterranean resort town of Nahariya, about 10 miles south of the Lebanese border, and on Kiryat Shemona, an Israeli development town in the Galilee panhandle.

In terms of casualties, it was the worst shelling on Israel in more than three years. The last Israeli fatality from a rocket attack occurred in Kiryat Shemona on Dec. 21, 1978, according to the Army command. On Nov. 8, 1977, one Israeli civilian was killed and five were wounded in a rocket attack on Nahariya.

The rocket attack appeared to be in retaliation for a series of air strikes against Palestinian positions in Lebanon yesterday that, according to reports from Beirut, killed five and wounded at least 18. During the 90-minute Israeli bombing raid, concentrated near the coastal town of Damour and the southern market town of Nabatiyeh, a Syrian Mig23 fighter that attempted to intercept the Israeli jets was shot down.

Uri Porat, press adviser to Prime Minister Menachem Begin, said that reports of the Katyusha rocket attacks in the Galilee was passed to Begin as he met in his home with his Cabinet to give formal approval to the multinational peacekeeping force to be stationed in the Sinai Peninsula once Israel completes its withdrawal next April.

Porat told reporters the rocket attack was "not unexpected" because Palestinian guerrillas in southern Lebanon yesterday suffered a "serious, heavy blow" as a result of the Israeli air strikes.

The Air Force attacks yesterday, Porat said, singled out the Popular Front for the Liberation of Palestine -- General Command, headed by Ahmed Jabril. This group was responsible for today's rocket attacks on Nahariya and Kiryat Shemona, he added.

[In Beirut, a military spokesman for Palestinian and leftist forces said they had scored direct hits on artillery positions in Nahariya, Kiryat Shemona, Misgav Am, Metullah and Kfar Yigal, as well as the Lebanese town of Marjayoun, held by Israeli-backed Lebanese rightists. In a statement quoted by the Palestine news agency Wafa, he said the Israelis had first shelled areas around the southern Lebanese towns of Nabatiyek, Tyre and Sidon.]

Israeli Army officials said they had no information on where the rocket were fired.

Police officials in Nahariya said the first rocket barrage struck at about 5:30 p.m., when streets were crowded with people leaving work and returning to their homes. Two Israeli civilians driving in a car were killed and another was killed while walking in the street, police said. All the injured were pedestrians, officials said.

Police cut all traffic to the town and many residents went to bomb shelters for the night.

In Kiryat Shemona, a Katyusha scored a direct hit on an apartment block, injuring five persons, police said.

On Friday, several hours after Israeli Air Force planes also struck Palestinian targets in southern Lebanon, more than a dozen Katyushas fell on Kiryat Shemona, destroying a synagogue and damaging apartment buildings. Fourteen persons were reported injured.

An hour after tonight's first barrage fell on Nahariya, several other rockets struck the town. Several persons were injured.

The Israeli Army command said its artillery along the border opened fire early this evening against positions where the Israelis suspected the Katyusha attack originated.