MANILA (UPDATE) - The military on Saturday said 13 government troops were killed on Friday evening in offensives against Islamic State-linked terrorists in Marawi City.

Philippine Army 1st Infantry Division spokesperson Lt. Col. Jo-Ar Herrera said the fatalities were Marines who were rescuing trapped civilians in conflict-torn Marawi City.

"We are saddened with the result that we have fatalities in the government side. We have incurred 13 killed in action and we are still awaiting the reports pertaining to the wounded in action," Herrera said in a press briefing.

Herrera said troops had difficulties in rescuing trapped civilians since extremists were well-positioned in mosques and were using civilians as human shields.

"Ang key component na nakita namin dito during the firefight of the Marines, talagang ginagamit ng local terrorist group yung mosque. Dun talaga nakapwesto yung kalaban," he said.

Military sources meanwhile told ABS-CBN News that at least 51 soldiers were wounded in the said firefight. Sources also said troops encountered trouble in locating terrorist snipers still positioned around the city, given the urban terrain.

The fresh wave of casualties on the government side came hours after military officials announced their plan to liberate Marawi City from terrorists on June 12, the Philippine Independence Day.

The attack also came on the heels of the arrest of the Maute family's matriarch, Ominta Romato "Farhana" Maute, on Friday afternoon.

Farhana and two other injured Maute group members were arrested after their vehicle was intercepted in Brgy. Kormatan, Masiu town, ARMM Regional Police Director Reuben Theodore Sindac said.

Sources said Farhana, mother of terror leaders Omar and Abdullah Maute, was the group's courier, financier, and link to foreign terror groups.

Her arrest may either demoralize Maute group members or may push the group to become more aggressive, sources said.

The Maute's patriarch, Cayamora Maute, was also apprehended Tuesday morning at a checkpoint in Sirawan, Toril, Davao City.

Clashes between government troops and Maute and Abu Sayyaf group terrorists broke out on May 23, as state forces attempted to arrest terror leader Isnilon Hapilon, known to be the anointed Islamic State chief in Southeast Asia.

Video found by the military showed that Hapilon and other terror leaders planned to carry out attacks in the city days before firefights began.

The firefights prompted President Rodrigo Duterte to declare martial law over the entire island of Mindanao on the same day the fighting broke out.

More than 200 have died in the firefights, while over 230,000 residents have fled the city since clashes began. -- reports from Chiara Zambrano, ABS-CBN News