Israeli forces staged a major raid into Lebanon before daylight this morning and destroyed four Palestinian artillery bases, a military spokesman announced.

An unspecified number of paratroopers, infantry troops and members of the engineers corps crossed the Israeli-Lebanese border by foot and over the Litani River a few miles away, the spokesman said. The troops, he added, were returned home by helicopter.

The military said several Palestinians were killed in the raid and the Istaelis suffered casualties. Under a government policy, the exact number of casualties were not reported.

The raid took place on the Arnoun Plateau, a steep mountainous region overlooking areas held by the Lebanese Christian militia, which is supported by Israel. The last time Israeli troops raided into the area was January 1979.

The troops had to pass through U.N. peacekeeping positions to reach the region.

The Israeli defense forces said that after dawn aircraft "heavily bombed" a Palestine Liberation Organization stronghold in Beaufort Castle, just north of the Litani River. The Crusader-era castle has long been used by guerrillas by Christian militias led by Maj. Saad Haddad, and generally has been considered impregnable to attacks.

The Israeli spokesman said the raid was a "preventative measure" to "foil the [Palestine Liberation Organization] and prevent its strikes." He said guerrilla artillery batteries, mortars and antiaircraft positions were destroyed in the raid, as well as several buildings. The bases were at Hama, Tibnit, Attahar and Mazra, he said.