A Palestinian brother and sister have been killed in Gaza when they were hit by fragments from an Israeli missile.

Residents of Beit Lahiya in the northern Gaza Strip said Yassin Abu Khoussa, 10, died after debris from the explosion hit his home, which is situated next to a militant training camp.

His six-year-old sister, Israa, who was seriously wounded, later died in hospital, Gaza health ministry spokesman Ashraf Al-Qidra said.

Saturday's incident took place hours after militants launched rockets into Israel.

Israel says its planes targeted militant training camps belonging to Hamas, after four missiles landed in southern Israel.

There were no casualties on the Israeli side.

Israeli military spokesman Lieutant-Colonel Peter Lerner said the rocket strike was an effort by militants 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."

Gaza rocket fire has tapered off significantly since the 2014 war when militants fired thousands of rockets and mortar rounds into Israel. Israeli attacks killed more than 2100 Palestinians, mostly civilians, while Palestinian fighters killed six Israeli civilians and 67 soldiers.

Beset by a months-long surge of street attacks by Palestinians from the occupied West Bank and Jerusalem, Israel has little desire to see a new flare-up in Gaza, where Hamas has mostly held its fire in the past 18 months.