Civilians held hostage by Islamist militants occupying a southern Philippine city have been forced by their captors to loot homes, take up arms against government troops and serve as sex slaves for rebel fighters, the army said on Tuesday, June 27, Reuters reports.

Citing accounts of seven residents of Marawi City who either escaped or were rescued, the military said some hostages were forced to convert to Islam, carry wounded fighters to mosques, and marry militants of the Maute group loyal to Islamic State.

"So they are being forced to be sex slaves, forced to destroy the dignity of these women," military spokesman Jo-Ar Herrera told a news conference.

"So this is what is happening inside, this is very evident ... these are evil personalities."

Their accounts, which could not be immediately verified, are the latest harrowing stories to come out of a conflict zone that the military has been unable to penetrate for five weeks, as well-armed and organized rebels fight off soldiers with sniper rifles and rocket-propelled grenades.

Some escapees say bodies of residents have been left in the streets, some for weeks, and civilians are distressed by government air strikes and artillery bombardments that have reduced parts of Marawi to rubble.

The protracted seizure has worried the region about the extent the Islamic State's agenda may have gained traction in the southern Philippines, which is more used to banditry, piracy and separatism than radical Islam.

The rebels' combat capability, access to heavy weapons and use of foreign fighters has raised fears in the mainly Catholic country that the Marawi battle could just be the start of a wider campaign, and be presented by Maute as a triumph to aid their recruitment efforts.