manila philippine president rodrigo duterte saturday rule possibility allow islamic state-linked militants flee southern city exchange release dozens hostages militants seize large part marawi city island mindanao may hardcore fighters hold 100 days air strike grind attack troop way duterte tell reporters ask rumor one rebel leader omarkhayam maute propose release hostages exchange safe exit militants pocket fighters remain ruin heart city devastate artillery bomb occupation alarm region possibility islamic state back foot iraq syria make new home southern philippines military launch final push retake marawi come heavy fire gunmen troop try secure build navigate mine booby-traps military estimate 20 30 hostages hold say force take arm government troop save one life will wait one year retake city duterte say hostages visit wound soldier cagayan de oro hours away marawi martial law impose mindanao island 22 million people end year allow military break alliance pro-islamic state militant group another front military also fight communist rebel new people army follow breakdown peace talk government duterte saturday threaten expand martial law areas philippines crack insurgents 655 militants 45 civilians 145 soldier policemen kill marawi accord military say rescue 1,728 civilians least 400,000 displace army spokesman colonal edgard arevalo say save hostages priority military mission still mindful presence civilians -guns head make human shield order wield firearms ammunition convert become fighters shoot troop say statement unite state provide technical support philippines military marawi visit manila friday australian defence minister marise payne offer small detachment soldier provide train philippine force philippine leader say 'no way 'll deal islamist rebel