MANILA, Philippines -- The Philippine president says he won't talk to militants aligned with the Islamic State group and has ordered troops to kill them even if the gunmen slaughter their hostages in a besieged southern city.

President Rodrigo Duterte issued his strongest warning yet late Sunday to local and foreign militants who laid siege on Marawi starting May 23, saying he has lost too many soldiers and policemen to the violence and won't let that pass.

The military says 178 combatants and civilians have been killed in Marawi, the heartland of Islamic faith in the country's south, after hundreds of gunmen waving Islamic State-style black flags rampaged across the city, burning buildings as they battled troops who were backed by airstrikes and artillery fire.