The video, aired by GMA television late Thursday showed a mud-splattered captive, dressed only in shorts, surrounded by soldiers in Marawi.
The video, aired by GMA television late Thursday showed a mud-splattered captive, dressed only in shorts, surrounded by soldiers in Marawi, where a five-month battle between troops and Islamic State followers ended this week.
As the captive is taken away with his hands being held behind his back, some of the soldiers rushed towards him, punching and kicking him as one is heard yelling out: "You killed a lot of people, idiot".
Military spokesman Major General Restituto Padilla, commenting on the video on Friday, said an investigation into the incident was underway to find out who was involved.
"The armed forces (are) very strict regarding the treatment of captives in a conflict situation. They are suppose to be decently treated and respected, which did not happen in this case," Padilla told reporters.
The video emerged after the military declared on Monday the fighting over, exactly five months afer it began when IS supporters rampaged through the city and then sought to occupy it.
The fighting claimed the lives of 920 militants, 165 troops and 42 civilians, according to the military.
US Defence Secretary James Mattis, while in the Philippines, on Wednesday praised local troops for upholding human rights during the Marawi conflict.
"I think the most important thing is here's an army that had to go in a fight like that, and they had not one human rights allegation against them with any credibility, not one," Mattis told reporters
Padilla described the incident as an "isolated case".
"We are not hiding this," he said, adding the results of the investigation would be made public and those responsible held accountable.
But he also appealed for understanding, saying emotions ran high in the battlefield especially after soldiers were killed.
He also called on the public not to share such videos, saying the militants could use them as propaganda.