13 Marines killed in latest Marawi clashes — AFP

Metro Manila (CNN Philippines) — Thirteen Marines were killed in what could have been the most intense firefight in Marawi on Friday.

Among them was 1st Lt. Frederick Savellano, a platoon commander of the team that recovered the ₱52 million in cash and ₱27 million worth of checks in a house defended by Maute fighters.

In a press briefing Saturday, Joint Task Force Marawi spokesperson Jo-ar Herrera said the terrorist group used human shields in the "intense firefight."

"Ang goal talaga ng Marines is to facilitate the rescue of hostages that were held in that area," Herrera said, "So while they were conducting combat-clearing operations, ang ginawa ng local terrorist group ay naglagay sila ng IED (improvised explosive device), naglagay sila ng B40 and RPGs (rocket-propelled grenades) in the area."

[Translation: The goal of the Marines is to facilitiate the rescue of hostages that were held in that area. So while they were conducting combat-clearing operations, the local terrorist group placed IED, B40, and RPGs in the area.]

READ: Military hopes to liberate Marawi by Independence Day

He added they are still verifying the number of injured troops.

The casualties were members of Marine Battalion Landing Team-7, which was deployed to Marawi on June 1.

This now brings the total figure of government troops killed in action at 58. AFP is still verifying the number of casualties on the enemy side.

Herrera said government forces are inching toward liberating the embattled city.

"The troops continue to gain more foothold into the inner areas of the city, clearing of areas by by sector progressing positively," he said.

He assured the military is committed to saving the civilians.

READ: Government orders arrest of 185 terror group members on rebellion charges

"We will continue to execute our mandate by conducting combat-clearing operations of the affected areas, and we will ensure that we save lives through expeditious military action," Herrera said.

He also confirmed earlier reports that operatives from the United States are now helping the Armed Forces.

Herrera then clarified the U.S. special forces are not joining the firefight, but are instead facilitating technical support and training.

Terrorists strategically positioned

Two Marine officers, who spoke with CNN Philippines on condition of anonymity, recounted the Friday encounter.

"Naghihiwalay-hiwalay sila. Tapos nagbubutas sila ng semento at doon nila aabangan ang tropa. Tapos occupy-in nila siyempre yung matataas na building. Hindi mo rin sila pwedeng lapitan kasi mataas sila. Tapos try mo buksan ang pinto, di din mabuksan," said one of the Marine officers.

[Translation: They were scattered. They were poking holes in the cement where they monitor that roops. They also occupy the tall buildings, so we could not get close. We also could not open the doors.]

The officers said the terrorists were heavily armed and strategically positioned at the city center.

"Delikado talaga. Kasi very accurate ang snipers' rifles nila. Kahit ganon pa man, kahit malakas ang resistance nila, hindi yun ang naghadlang sa atin para matakot tayo doon. Actually, mas motivated tayo," said another Marine officer.

[Translation: It was really dangerous because the snipers' rifles are very accurate. However, even their strong resistance wouldn't stop and scare us. Actually, we are more motivated.]

Despite the casualties, the Armed Forces said they inflicted heavy damage on terrorists.

Maute brothers killed?

In the press briefing, Herrera said they are still verifying reports of the death of two Maute brothers in a separate firefight.

"There are reports that Omar and Madie were killed in the operations. We are still validating this report, but [there are] strong indications that they are killed," Herrera said.

Omar and Abdullah Maute were the leaders of the terror group that attacked Marawi. Madie Maute was involved in planning, along with former Abu Sayyaf leader Isnilon Hapilon.

Herrera said according to reports, Hapilon is still in the area.

READ: Mother of Maute brothers arrested in Lanao del Sur

The reported death of the Maute brothers comes in light of the ealier arrest of their parents.

"The arrest of the parents is part of the security measures that we have implemented. They were separately arrested, this is a part of our tactical plan to neutralize all terrorists, including their supporters," Herrera said.

Their father, Cayamora Maute, was arrested in Davao City on June 6. He claimed to have no knowledge of the Marawi attack and the group's link to the international terror group Islamic State (ISIS).

READ: Father of Maute brothers arrested in Davao City

Meanwhile, Ominta Romanto Maute, also known as Farhana, mother of the Maute brothers, was nabbed at a safe house in Lanao del Sur on June 9.

"This is another milestone in our operations because historically, the parents, especially Farhana, provides logistical, financial...and she has the limbs to international organizations. So basically, if you cut of the head, it will have an impact to that organization," Herrera said.