Jerusalem ? Israeli jets and artillery pounded Palestinian and Lebanese guerrilla targets in Lebanon on Sunday after rockets hit an army base in northern Israel. It was the harshest military response by Israel since it withdrew its forces from southern Lebanon six years ago, the military said.

In daylong fighting, Israeli forces exchanged fire with guerrillas from the Iranian-backed Hezbollah group along the length of the border with Lebanon, and residents in northern Israeli communities were ordered into bomb shelters as mortars and rockets fell in the area.

A cease-fire was mediated by U.N. peacekeepers at the request of the Lebanese government, the army said.

The flare-up followed Friday’s killing in Lebanon of a leader of the militant Islamic Jihad group and his brother in a car bombing in the southern town of Sidon, an attack the group blamed on Israel.