Hamas has acknowledged that about a third of Palestinian casualties in the Israeli military operation in the Gaza Strip comprised fighters of the Islamic insurgency movement. Hamas said 25 members of the Izzedin Kassam military wing were killed in the week-long Israeli military operation in the northern Gaza Strip. In a communique, Hamas said one of the insurgents was the brother of the movement's spokesman, Mushir Al Masri. "Our rifles will stay aimed at the enemy as long as it occupies our land," Hamas said. "Our martyrs were killed in these days of rage witnessed in the northern Gaza Strip. Our response to these massacres won't take too long."Hamas's acknowledgement of casualties came as Palestinian sources reported a debate within the insurgency group whether to appeal for a ceasefire. The sources said the Palestinian Authority urged Hamas to agree to end missile attacks on Israel in exchange for a withdrawal of the military from the northern Gaza Strip. Palestinian sources said about 80 Palestinians have been killed in the Israeli military operation. They said more than a third of the casualties were civilians. On Tuesday, two Palestinians were reported killed in fighting in Jabalya. The Israeli group B'Tselem asserted in a report that 40 percent of the Palestinian casualties in the current Israeli military operation were civilians. Israel's military said the lion's share of Palestinian casualties were armed combatants and that insurgents were using civilians for cover. On Tuesday, Israeli main battle tanks, attack helicopters and troops focused their operations in Bet Hanoun and the Jabalya refugee camp. The camp has about 90,000 residents and regarded as the stronghold of Hamas and the focus of Kassam-class short-range missile production.