MANILA — The Philippine Justice Department filed murder charges on Monday against three police officers in the death of a 17-year-old boy last year, a case that strengthened opposition to President Rodrigo Duterte’s brutal war on drugs.

The officers — Arnel Oares, Jeremias Pereda and Jerwin Cruz — were charged in a lower court in Caloocan City, north of Manila, along with an informant who had erroneously identified the boy, Kian Loyd delos Santos, as a drug pusher.

Witnesses had described seeing Mr. delos Santos being dragged away by the officers and finding his body slumped over near a pigsty. That contradicted statements by the police officers, who said the boy had pulled a gun, setting off a shootout in which he died.

The teenager’s death in August ignited public anger, and his funeral procession became a protest led by the influential Catholic Church and activists who denounced Mr. Duterte’s drug crackdown.