Israel ? Israel’s prime minister on Sunday gave his military a “free hand” to attack Gaza militants after a rocket slammed into a house after the visiting U.N. humanitarian chief had just called for an end to the daily salvos.

Prime Minister Ehud Olmert said he would not allow a humanitarian crisis to develop in Gaza, but the people there could not live normal lives while Israelis across the border were constantly targeted by rockets.

Olmert spoke at a gathering of the Conference of Presidents of Major American Jewish Organizations in Jerusalem.

Early Sunday, Israeli ground forces backed by aircraft entered Gaza. Three Palestinian militants and a civilian were killed in clashes, and an Israeli soldier was seriously wounded. More than 20 people were wounded, including several gunmen and a 45-year-old civilian who was shot in the head, Palestinian health officials said.

The military said the target was the Gaza “terror infrastructure,” and more than 80 Palestinians were taken for questioning.

John Holmes, the U.N. undersecretary general for humanitarian affairs, had just left Sderot, where he made an appeal for an end to the rocket fire from Gaza, when a rocket exploded in a house there.