The rockets struck the southern city of Beersheba and Ashdod in the west on Wednesday.
The attacks came one day after 10 Palestinians, including four children, were killed in Israeli airstrikes and shelling on the eastern outskirts of Gaza City.
The Islamic Jihad’s armed wing, al-Quds Brigades, said the rockets were fired in retaliation for the “Zionist massacres against our men of resistance and against our people in the Gaza Strip.”
Shortly after the rockets landed in the occupied territories, Israeli warplanes launched airstrikes east of Gaza City where Palestinians were mourning those killed in Israeli attacks the day before.
There were no immediate reports of casualties.
Hamas Prime Minister Ismail Haniya has called on the UN Security Council to take action to protect Palestinians against Israeli attacks.
Israel has imposed a deadly siege on the Gaza Strip since June 2007, when Hamas, the democratically-elected government of Gaza, took control of the tiny Palestinian territory.
The blockade has had a disastrous impact on the humanitarian and economic situation in the strip.