The attack Monday afternoon occurred in Israel’s Eshkol region, located along the border with Gaza.
At least nine injured people were airlifted to Soroka Medical Center in Beersheba. Two reportedly are in serious condition.
The Code Red siren did not sound, as mortars do not usually set it off.
The killed and injured were visitors to the area, according to the Jerusalem Post, citing a spokeswoman for the Eshkol Regional Council.
The head of the Eshkol Regional Council, Haim Yellin, called on Israeli civilians to stop visiting soldiers in the area.
Roads into the area remain closed to traffic.
The unofficial cease-fire between Israel and Gaza seemed to come to an end Monday evening as at least 12 volleys of rockets were fired at Israel. Code Red sirens sounded though out the Carmel region in northern Israel, including areas such as Zichron Yaakov, Hadera and Caesarea.