Marawi - The Philippines military has uncovered five decapitated bodies of civilians among a total of 17 dead bodies found in Marawi City. The macabre find comes amid reports of widespread looting and sex slavery by Islamic State-affiliated Maute fighters. The civilian death toll in the fighting stood at 27 before this latest discovery, which is the first such instance of the Islamist militants employing such extreme tactics against civilians. Authorities fear the civilian death toll may further rise. "[It] may increase significantly once we are able to validate all this information," military spokesman Restituto Padilla said, as cited by Reuters. "There have been a significant number [of dead bodies] that have been seen but again, we cannot include many of these," he said. "Our combat environment is sensitive. First, there are trapped civilians that we have to protect. They also have hostages and third, there are many traps so we have to clear buildings slowly," he said. Civilian hostages in the besieged city have also reportedly been forced into slavery by the militants, who have been holed up for almost six weeks in the battle against the country's military.