The Israeli military says Hamas and other armed groups have fired more than 2,800 rockets from Gaza in six days.
Many of the rockets have been intercepted by Israeli anti-missile systems, while some have fallen short of the border.
Israeli air strikes on Sunday killed 33 Palestinians, including eight children, Gaza health officials said, as militants fired an early morning barrage of rockets into Israel.
The death toll in Gaza overnight jumped to 181, including 47 children, amid an intensive Israeli air and artillery barrage since the fighting erupted last Monday. Ten people have been killed in Israel, including two children.