Five hundred militants were involved in the siege of the southern Philippines city of Marawi, and the extremists had a “big plan” to occupy the area, the country’s defense chief said Thursday. Defense Secretary Delfin Lorenzana’s comments came as the country’s military entered into its second week of fighting to retake the city, with at least 25 soldiers and 19 civilians reported killed since last Tuesday. Amid fears that the militants were seeking to spread ISIS’s foothold to the Philippines, Lorenzana said foreign fighters were among those killed, with Chechen and Arab fighters identified. Between 50 to 100 militants remain in the city, he said. Philippine authorities said earlier Thursday that 11 of its soldiers were killed in a “friendly fire” airstrike meant for the militants. An air force plane targeting the extremists accidentally hit government troops fighting with the militants, a military spokesman said Thursday. An investigation has been ordered into that incident, the spokesman said, partly to prevent any further “friendly fire” situations as government forces continue to battle with more than 30 assault aircraft.