Israel struck back at Hamas Friday for a rocket attack launched the day before targeting an Israeli school bus.
Israel Defence Forces aircraft and ground troops reportedly killed six Hamas militants and five civilians.
Gaza militants fired 16 rockets and mortars at southern Israel Friday, causing no injuries, the Israeli military said.
Hamas has admitted it was behind the school bus attack. Most of the school children had exited the bus when the rocket struck its target.
Israeli Prime Minister Benjamin Netanyahu said the attack on the school bus "crossed a line" and warned that "whoever tries to harm and murder children will pay with their life."
For the second day in a row, Israel's cutting-edge Iron Dome missile defense system successfully intercepted a Palestinian rocket aimed at an Israeli city, the military said.
Hamas said the rocket attack was in retaliation for the killing of three fighters in an airstrike earlier in the week.
U.N. Secretary-General Ban Ki-moon condemned the bus attack and expressed concern over civilian casualties in Israel's strikes.
He called for "de-escalation and calm to prevent any further bloodshed."