A technical failure in the artillery's radar system was to blame for Wednesday's tragedy in Beit Hanun, the IDF announced Thursday night. A failure in the targeting mechanism caused seven shells to stray from their intended trajectories, resulting in the deaths of 19 Palestinian civilians, said Maj.-Gen. Meir Klifi, who headed the investigation into the incident. In light of the inquiry, Defense Minister Amir Peretz ordered Thursday evening that all artillery fire into the Gaza Strip must first be approved by OC Southern Command Maj.-Gen. Yoav Galant. Meanwhile, Chief of General Staff Lt.-Gen. Dan Halutz ordered a halt to all artillery fire aimed at Gaza until further technical, professional and operational inquiries are completed, the IDF Spokesman's Office said. "The chief of General Staff emphasized that the IDF operates solely against the terrorist infrastructure and uses all means at its disposal to avoid targeting uninvolved civilians. The chief of General Staff expressed his regret for the civilian casualties as a result of the technical failure," its statement read. Speaking with reporters soon after submitting the results of his investigation to Halutz and Defense Minister Amir Peretz, Klifi, who is deputy OC Ground Forces Command, said his team found that the "Shilem System" kit had been installed in the cannon by IDF technicians five days previously. It was tested in live firing exercises, and checked again by technicians 11 hours before its use Wednesday, Klifi said. The kit had been in use since the 1980s and after "hundreds of thousands" of firings showed a margin of error of 25 meters, Klifi said. However, for reasons that are not entirely clear, the system failed - with tragic results. Nineteen members of an extended family were killed, including many women and children, and some 50 others wounded when the errant shells tore through an apartment complex. The attack outraged the international community, and Israel was placed on heightened alert in anticipation of reprisals by the terror organizations. Klifi said instruments on the cannon showed a variation of 200 meters immediately after the shelling, but that the margin could have been larger because of the faulty kit. He said his probe found that at least two homes in Beit Hanun showed evidence of having been directly hit. All the evidence of the inquiry indicated that the civilian casualties were caused by IDF artillery, Klifi said. Peretz reiterated his regret for the tragic accident and, in an effort to aid the victims, he ordered the Rafah border crossing to be opened until 5 p.m., with preference given to ambulances, medical and humanitarian aid entering the Gaza Strip, according to a statement from the Defense Ministry. The crossing had been closed due to intelligence of plans to attack the installation. But the Palestinians were unswayed by Peretz's apology, and Kassam cells targeted Sderot through out the day, launching five rockets into the town. One Kassam scored a direct hit on a store at 6:50 p.m., spraying shrapnel that lightly wounded three people, the army said. Earlier, two Kassam rockets landed in one the kibbutzim in the Eshkol Regional Council. No one was wounded, but some of buildings were damaged. Three others rockets struck open areas. Security forces, meanwhile, braced for Palestinian reprisals inside the Green Line, and security sources said there are currently 80 warnings of plans to carry out attacks. They said there is intelligence of 15 specific cells that are in the final stages of preparation for attacks ranging from suicide bombings to kidnappings. The current alert level is six - the maximum - a police official said. Meanwhile, demonstrations in east Jerusalem and Hebron turned violent as Palestinians took to the street to protest the botched artillery strike. Residents of east Jerusalem closed businesses and schools in solidarity with a three-day mourning period decreed by Palestinian Authority Prime Minister Ismail Haniyeh, and spontaneous demonstrations broke out inside the Old City and in Arab neighborhoods. Hundreds of youths rallied at the Damascus Gate and near the Temple Mount, where they chanted anti-Israel slogans and threw stones at border policemen. Anticipating disturbances in the area, police reinforced their presence, and the Temple Mount compound was closed for closed for close to an hour. When the rioters turned their rage against the police station near the Western Wall, police dispersed the angry crowd with stun grenades. In separate incidents on on Sultan Suleiman and Salah a-Din streets, youths bombarded police with stones and debris, slightly injuring two officers, and at a gas station in Isawiya, youths hurled stones from inside a bus at police on patrol. When the police stopped the bus, the youths attacked the officers before police subdued them and arrested four believed to have thrown the stones. Jerusalem police said they were planning to maintain a heavy presence during Friday prayers on the Temple Mount in light of intelligence information that activists planned to disturb public order there. They announced that entrance to the compound would be permitted only to those men presenting an Israeli identity card who were older than 45, and to women of any age with Israeli identity cards. Rebecca Anna Stoil contributed to this report.