Fragments from a missile fired by an Israeli aircraft killed a 10-year-old Palestinian boy and his sister in Hamas-controlled Gaza, Medical officials said on Saturday.
The Israeli military said in a statement that it had targeted four Hamas training camps after rockets reportedly fired from Gaza landed in open areas in southern Israel late on Friday but no casualties were reported.
Yassin Abu Khoussa died after missile debris hit his home, which is located next to a training camp, residents of Beit Lahiya in the northern Gaza Strip said.
His six-year-old sister, Israa - who was seriously wounded - later died in hospital, Gaza Health Ministry spokesman Ashraf al Qidra said.
Israeli military spokesman Lieutenant-Colonel Peter Lerner said the rocket strike was an effort to "threaten the security and safety of the people of southern Israel. The [military] will continue to act to protect against those who threaten innocent lives and Israel's sovereignty."
The fatalities from air strikes in Gaza are the latest since last October.
More than 2,100 Palestinians were killed in the 2014 Israeli offensive on Gaza.