Israeli helicopters Thursday fired on a Shiite Amal military base in southern Lebanon and wounded at least eight militiamen in retaliation for an attempted Palestinian guerrilla infiltration into northern Israel a day earlier.

The helicopters attacked the site north of the village of Tibnin outside Israel's "self-declared" security zone in an area of southern Lebanon controlled by the Amal militia, an Israeli army spokesman said.Wednesday, three gunmen from the Syrian-based Palestinian Liberation Front were killed by Israeli soldiers along the border fence near Kibbutz Menara. The army spokesman said the base it attacked "was used by the Amal to assist the activities of the terror ring," referring to the guerrillas who made the infiltration attempt.

At least nine guerrillas have died in the last five days during three attempts to penetrate Israel.

The United Nations Interim Forces in Lebanon, which patrols the territory where the raid was staged, reported that eight Amal militiamen were wounded, six seriously. An Amal source said 10 to 12 militiamen were wounded.

The choppers made predawn sweeps over the vast southern area before opening fire after sunrise, hitting a four-story building near Soultanieh used as a base by the pro-Syrian Shiite Amal movement, police in the southern port city of Sidon said.

Militiamen returned fire, Beirut radio said, but the Israeli army reported all its aircraft returned safely.