Two Palestinian children were reportedly killed Saturday as the result of an Israeli airstrike in the Gaza Strip in response to rocket fire into Israel on Friday.

According to Palestinian sources, the two, a brother and sister aged 6 and 10, lived in a small shack in northern Gaza's Beit Lahia. The boy died immediately after the strike late Friday, while the girl suffered serious wounds and died Saturday.

Open gallery view Body of Yassin Saliman Abu Khousa, a Palestinian boy killed after his house was hit by fragments from an Israel missile fired in response to rocket fire, in northern Gaza Strip. March 12, 2016. Credit: AFP

They were identified as Yassin Saliman Abu Khousa and his sister Issra; their 13-year-old brother was also wounded in the air strike, Palestinian sources said.

Hamas' military wing, the Izz ad-Din al-Qassam Brigades, said in response that "it's patience towards Israeli crimes has limits," and warned that "the two children's blood was not spilt in vain."

Gaza officials said they believe a Salafist group opposed to Hamas is responsible for the rocket fire into Israel on Friday.

On Friday, four rockets were fired from the Gaza Strip hit open areas in south Israel. No casualties were reported. The Color Red rocket alert sounded in communities near the border with Gaza.

Israel responded to the rocket fire by attacking four Hamas targets in the northern Gaza Strip from the air.

At the same time, two Israeli soldiers were lightly wounded in a shooting attack at a West Bank checkpoint.