The head of the Arab league on Thursday warned of a "disastrous outcome" if the bloody infighting between Hamas and Fatah continues, and urged an immediate cease-fire. "I call for a cease fire immediately," Amr Moussa said in Cairo after an urgent meeting with Jibril al-Rajoub, Palestinian Authority Chairman Mahmoud Abbas's senior security adviser. Moussa urged the Palestinian factions embroiled in what looks increasingly like a civil war in the Gaza Strip to "cooperate more" with an Egyptian team of mediators. At least 15 Palestinians were killed on Thursday as Hamas overran one of Fatah's most important security installations in the Gaza Strip on Thursday. Moussa also said that the Arab states were "extremely displeased" at the Palestinian clashes, which he described as "unacceptable." The Arab League was preparing for holding an urgent Arab foreign ministers' meeting on Friday to discuss the deteriorating security situation in the Palestinian territories, Moussa said. Al-Rajoub said what was needed now was a "constructive, unified Arab stance to rescue the Palestinians from this destruction." He warned that if the fighting weren't halted, it would make all the Palestinians "losers." Earlier Thursday, the European Commission suspended its humanitarian aid projects in the Gaza Strip, citing the escalating sectarian violence. "I fervently hope that the projects can resume very soon," said EU Humanitarian Aid Commissioner Louis Michel. EU humanitarian operations in both Gaza and the West Bank totaled 84 million euros ($110 million) last year. So far this year, it has earmarked 60 million euros ($80 million). Some 80 people, most of them armed, have been killed since a spike in violence Sunday sent Gaza into civil war. "This is a time when people desperately need protection and support. The warring parties must respect the principles of international humanitarian law," said Michel. Despite the escalating violence, EU External Relations Commissioner Benita Ferrero-Waldner called on the Palestinians to stick with a national unity government. "Now is not the time to give up on national unity, both in the government and in the security sector," she said. "I call on both Hamas and Fatah to invest all their energy in this coalition. "