At least 23 fighters were killed in clash between two Muslim rebel factions in the southern Philippines that started early this week, a military report said today. The fighting erupted Tuesday between the main Moro Islamic Liberation Front and a group led by rogue MILF commander Umbra Kato, the report said. More than 2,500 people have fled their homes in the towns of Datu Piang and Guindulungan town in Maguindanao province, 960 kilometers south of Manila, where the clashes were concentrated.