Daesh leadership in battle zone 'crumbling' due to depleting resources and communication breakdown, army spokesman says.

A military official on Monday expressed confidence that government victory over the Daesh-linked Maute group in Marawi was "irreversible".

In a press briefing in the besieged city, military spokesman Lt. Col. Jo-ar Herrera said that the militants leadership in the battle zone was already "crumbling" due to problems encountered such as depleting firepower and other resources and communication breakdown, ABS-CBN News reported.

"We have validated reports of leadership problems inside. They also lack ammunition," Herrera said.

"There is the issue of money, the issue of decision making," he added.

The government has cleared 86 buildings previously controlled by the militants, and Herrera said that the troops were "inch by inch moving towards the center of gravity".

The planned rescue of trapped civilians during the eight-hour Eid truce staged Sunday was aborted as militants continued firing. A child and four others were successfully recovered.

However, an official confirmed militants' beheading of hostages since they laid siege.

Death toll in the region as of Monday is 387 including 290 militants, 70 government troops and 27 civilians.

Meanwhile, Ana Zenaida Unte, an official of the Education Department said they were locating some 140 public school teachers from Marawi who were affected by the ongoing conflict in the area, according to GMA News.

Unte, however, clarified that these teachers might not be necessarily trapped inside the war zone.

The battle between the government forces and the Maute group in Marawi City prompted President Rodrigo Duterte to place all of Mindanao under martial law on May 23.