"We are still validating this report but there are strong indications that they [were] killed", he said in a press briefing.
"The chief of staff made an announcement, hoping, that by Monday we can freely wave our flags in every corner of Maraqi and we are working feverishly to do that", military spokesman Restituto Padilla told reporters.
"This temporary setback has not diminished our resolve a bit, " said military spokesman Col. Edgard Arevalo.
Meanwhile, Herrera confirmed the participation of USA military special forces in the government's fight against the Maute. Herrera said 13 marines conducting clearing operations died after an "intense" house-to-house firefight during which they encountered improvised explosive devices and were attacked by rocket-propelled grenades.
The fresh army fatalities raised the death toll from the government side to 58, while 138 extremists and 21 civilians were also killed.
It was among the heaviest fighting seen in mainly Muslim Marawi as the air force battered parts of the city with strikes to support ground troops.
"It instead primed up our determination to continue our prudent advances to neutralise the enemy, save the innocent lives trapped in the fight, and set the conditions for the rehabilitation and reconstruction of Marawi".
Filipino forces, meanwhile, captured on Friday the mother of two top militant leaders leading the siege. "They are just providing technical support", Lieutenant Colonel Jo-Ar Herrera said.
The Maute's patriarch, Cayamora Maute, was also apprehended Tuesday morning at a checkpoint in Sirawan, Toril, Davao City.
Military officials in the country said that a United States Navy aircraft provided surveillance for the local troops as the battle continued in Marawi on Friday.
Marine Commandant Maj Gen Emmanuel Salamat confirmed the casualties to GMA News website on Saturday (June 10), saying that government troops and militants from the Maute group had been involved in a 16-hour clash in Barangay Lilod Madaya that began at around 3.30am on Friday.
Family members of victims from a military plane crash prepare for a funeral ceremony in Dawei June 9, 2017.