UNITED NATIONS - The day of the death of ousted Libyan leader Muammar Gaddafi, who Libya's transitional government said was killed on Thursday, is a historic one for the Libyan people, UN Secretary-General Ban Ki-moon said."We have all seen the reports of the death of Colonel Muammar Gaddafi and the end of fighting in Sirte and other cities," the UN chief told a UN development conference. "Clearly, this day marks an historic transition for Libya.""Combatants on all sides must lay down their arms in peace," he added.