After two days of Operation Hot Winter - intense IDF activity on the outskirts of northern Gaza towns - Grad missile fire eased off on Sunday, although shorter-range Kassam rockets fired from the Strip continued to pound the western Negev. Givati Brigade infantry backed up by Armored Corps battalions began to search residential and public buildings in the "Kassam perimeter," the security zone over which the IDF first began to assert control a day earlier. Sunday's operations focused on the agricultural areas closest to the Gaza security fence, and the easternmost portions of Beit Hanun, Jabalya and Gaza City's Sajaya neighborhood. It is from this eastern perimeter that many Kassam cells have operated in recent months, as the proximity to the western Negev maximizes the limited range of the home-made rockets. But IDF sources said the much larger Grad missiles, brought in via Sinai, were being fired from farther inside heavily populated areas of the Gaza Strip, including from Gaza City itself. Soldiers reported that the enemy in northern Gaza was using a wide range of weapons, including improvised explosive devices, anti-tank missiles and snipers. Booby-traps were found in some of the houses, and in at least one case, soldiers discovered a weapons storehouse inside a mosque. The soldiers arrested around 30 Palestinians wanted for questioning. Two Palestinians were killed and two were wounded Sunday in an IAF strike in the northern Gaza refugee camp of Jabalya, Palestinian sources reported. According to the reports, 10 Palestinians had been killed in IDF operations since midnight Saturday, although it was unclear how many were gunmen and how many were civilians. Four soldiers were lightly wounded. Overnight Saturday, the IAF fired three missiles into the empty office building in Gaza City used by Hamas Prime Minister Ismail Haniyeh. The building was razed to the ground, and five people were lightly wounded, according to Palestinian sources. The IDF confirmed that Haniyeh's office had been hit, as well as seven weapons workshops and arms depots in northern Gaza. Hamas issued a statement following the attack on Haniyeh's office, saying Israel had "crossed a red line." A Grad missile hit Netivot for the first time on Sunday, albeit in a field on the outskirts of the western Negev town. The projectile struck meters away from the grave of kabbalist Rabbi Yisrael Abuhatzeira, also known as the Baba Sali. Residents have long believed that the grave protected them from the Kassam fire that plagued Sderot, their neighbor to the north. Meanwhile, Ashkelon received a partial respite from the Grad missiles it absorbed over the weekend. One Grad hit the city, tearing through the wall of a home in which a woman and her three grandchildren were sitting. Fortunately, in the four seconds between the time the "Color Red" siren was sounded and the instant the rocket tore into the side of the house, the four managed to run to a more secure interior room. The eldest child, a high-school-aged girl, suffered minor shrapnel wounds to her back. The Home Front Command continued to be active in Ashkelon Sunday, with teams dispatched throughout the city to assess the state of bomb shelters and to map out their locations. Defense Minister Ehud Barak and Deputy Defense Minister Matan Vilna'i approved the transfer of NIS 300 million to improve the state and availability of bomb shelters for the city's 120,000 residents. Residents of Sderot and the western Negev were somewhat less fortunate, with an estimated four dozen rockets striking in communities and in open areas. Four people suffered shrapnel wounds, and Sderot-based Magen David Adom teams treated 14 people for shock. The IDF is considering directing artillery fire at the source of rocket launchings. Barak is expected to convene a discussion on the legality of this tactic, since the rockets are frequently fired from residential areas. In the midst of the fighting, the Defense Ministry gave permission for a massive humanitarian convoy to enter southern Gaza through the Sufa crossing on Sunday afternoon. The Gaza Strip Coordination and Liaison Administration oversaw the delivery of 62 trucks, including three carrying medical supplies (bandages, water pumps, tourniquets, etc.), seven with World Food Program cooking oil, seven carrying sugar, nine bearing milk products, eight carrying fruit, two with water purification supplies and four with meat and fish products. It was the first such mission to go through the Sufa crossing in recent months. AP contributed to this report.