The Israeli security cabinet was to convene Saturday night to discuss a ceasefire proposal, as the military campaign entered its fourth week and airstrikes and artillery fire continued overnight and during the day across the Gaza Strip, according to dpa. In Cairo, Egyptian President Hosny Mubarak demanded an immediate ceasefire. "I call on the (Israeli) leadership for an immediate unconditional ceasefire and a complete withdrawal of Israeli troops from the Strip," Mubarak said in an address on national television. A Hamas spokesman in Lebanon said his organization would continue to fight the troops left in the coastal strip and until the blockade on the Gaza Strip was lifted. "As long as Gaza is occupied by Zionist soldiers the confrontations will continue, even if Israel approves a unilateral ceasefire," Osama Hamdan told Deustche Presse-Agentur dpa by phone. A unilateral ceasefire is supported by United Nations Secretary General Ban Ki-moon, who is visiting the region. "We need to find out if there are war crimes being committed," said Chris Gunness, the spokesman for UNRWA, the UN agency for Palestinian refugees, calling for an investigation. The UN's High Commissioner for Human Rights, Navi Pillay, said acts in the Gaza Strip "may constitute war crimes." Israeli Prime Minister Ehud Olmert's office on Friday said there had been "significant progress" in talks in Cairo. Israel and Hamas, the Islamist group which has de facto control of the Gaza Strip, do not talk to each other directly, negotiating instead through Cairo. The Egyptian government has been pushing for a ceasefire based on a short-term "humanitarian" truce, followed by negotiations on a longer-term ceasefire that would address Israeli security concerns and the militants' demand that the borders be opened.