Palestinian medics and hospital doctors said 23 Palestinians were killed in Israel's ground offensive since midnight, among them three Hamas gunmen.
Dr. Said Judeh of the Kamal Adwan hospital in the northern Gaza town of Beit Lahiya said eight people were killed in an Israeli artillery strike Sunday.
He said they were among a group of people trying to leave their homes for refuge in a nearby school. Beit Lahiya is scene of some of the heaviest fighting.
Health Ministry official Moawiya Hassanain Hassanain said that in the southern town of Rafah, a man and two teenage sons were killed in an Israeli airstrike.