Terrorists in Gaza fired several rockets at southern Israel on Friday, setting off warning sirens in Sderot and the Sha’ar Hanegev region. The rockets exploded in uninhabited areas, failing to cause injury or damage, the military said.In response, the Israel Air Force bombed four Hamas targets in the northern Gaza Strip early Saturday, the IDF Spokesman’s Office said.“The IDF views Hamas as being responsible for what occurs in Gaza, and will continue to act with severity to safeguard the quiet in southern community,” the military said.Defense Minister Moshe Ya’alon on Saturday night vowed to hold Hamas responsible.“We won’t tolerate attempts to breach the peace and to disrupt the lives of our citizens in the south,” he said at an event in Tel Aviv for wounded solders from the Armored Corps. “We responded firmly and harshly against Hamas. We will attack them more severely if such attempts [rocket launchings] continue,” Ya’alon said.Palestinian medical sources said fragments from a missile fired by the IAF killed a 10-yearold boy and his six-year-old sister in Beit Lahiya, in the northern Strip.Residents of Beit Lahiya named the boy as Yassin Abu Khoussar, and said he died when missile debris hit his home, which is situated next to a Hamas training camp. His sister was wounded, and later died of her injuries, the sources said.Israel Radio’s Palestinian affairs correspondent, Gal Berger, cited a senior Hamas member as warning Israel “not to test our patience.”Gazans last targeted southern Israel on January 24, when a rocket hit an open area in the Sha’ar Hanegev region.Islamic State-affiliated Salafi jihadist organizations are penetrating the Strip, and are believed to be behind all of the rocket and border bomb incidents in the past year and a half, IDF Chief of Staff Lt.-Gen.Gadi Eisenkot told a Tel Aviv security conference in January.“All of these groups challenge Hamas and seek to activate fire against us,” he said during a conference hosted by the Institute for National Security Studies.Reuters contributed to this report.