An Israeli army spokeswoman said the shelling on Monday was aimed at areas from which Palestinian militants had fired rockets at the Israeli town of Sderot, just across the Gaza border.
At least 151 Palestinians, around half of them fighters, have been killed in Israel's month-long assault on Gaza which it says is to recover a captured soldier and end cross-border rocket attacks.
Five rockets were fired from Gaza on Monday, the army spokeswoman said.
Al-Quds Brigades, the armed wing of the Palestinian group Islamic Jihad, said it had fired two rockets at Israel in retaliation for an Israeli airstrike that killed about 60 civilians in the town of Qana in southern Lebanon on Sunday.
"Our message to the criminal Zionists is that we will continue to bombard you until you leave our land or you face death and destruction," the group said in a statement.