Philippines hostages horrifically abused by IS captors
The military, citing accounts from residents of Marawi city, said some of the captives were forcibly converted to Islam and married to members of the Islamic State-linked Maute group.
"This is what is happening inside, this is very evident," army spokesman Jo-Ar Herrera told reporters.
"These are evil personalities."
The harrowing accounts emerge from an area that the Philippine army has struggled to liberate from militants after five weeks of fighting.
According to some escapees, the corpses of local residents have been left to rot in the streets for weeks.
The drawn out occupation of Marawi by the Maute group has raised concerns about the extent of the IS group's appeal and foothold in the southern Philippines.
It is feared that Maute's use of heavy weapons and foreign fighters to frustrate army forces could suggest the beginning of a wider campaign in the region.
Marawi, which is situated in the southern Mindanao region, has been reduced to rubble as the military campaign continues.
President Rodrigo Duterte has promised that Marawi will be rebuilt after the operation ends.
The president also expressed his anguish at the arrival of the IS ideology in the Philippines, saying that he could understand the motivations of Muslim seperatists but not the radical ideology of IS.
"What's painful for me, a fractured ideology entered. All that they want is to kill and destroy, how can we live with that?" he said.
Fierce clashes erupted on Tuesday in Marawi, as the battle to dislodge around 150 Maute gunmen who are controlling areas of the city continued.