Around 20 people were killed in a series of clashes between Muslim separatist guerrillas and government forces in the troubled southern Philippines, officials said on Tuesday. In the latest incident, a gun battle erupted when an army patrol encountered Moro Islamic Liberation Front (MILF) fighters near Mamasapano town on Mindanao island on Tuesday, local army commander Colonel Marlou Salazar said. The separatist fighters fled, leaving behind a heavy machinegun, a rocket launcher, a mortar and several rifles, he said.