The Code Red siren did not sound for the rockets fired from Gaza since it was known that they would land in open areas.
Palestinian officials say that Israeli airstrikes have struck militant sites in the Gaza Strip.
"Three bombs were dropped by the air force on a Hamas military base east of Nusseirat refugee camp", south of Gaza city, a Palestinian security source said, in reference to the Islamist movement that runs the Gaza strip. Israel considers Hamas a terrorist organisation.
Hamas spokesman Fawzi Barhoum described Israel's action as "unacceptable", accusing the Jewish state of a "continuation of this risky escalation against Gaza".
There was no immediate claim of responsibility for the projectile attack that exploded in the Sha'ar Hanegev Regional Council overnight, however the IDF holds Hamas responsible for any fire that emanates from Gaza.
However, Hamas militants continue firing rockets against Israel, while Israel is targeting Hamas positions in response.
"Four Palestinians sustained moderate injuries in the attacks", ministry spokesman Ashraf al-Qudra said in a statement. Israel has accused the United Nations body of cooperating with militants, while UNRWA has accused Israel of hindering its operations in the Gaza Strip. "I recommend that Hamas take responsibility, establish order and calm down".