MANILA, Philippines (AP) — The Philippine president said his threat to launch airstrikes against tribal schools because they allegedly teach subversion would apply only when the buildings are empty, a clarification that still raised concern he was advocating a war crime.

President Rodrigo Duterte responded to a question in a news conference late Thursday that the bombings will be done at night and maintained that the schools were teaching students to become subversives and were operating without government permits.

Still, Carlos Conde of the U.S.-based Human Rights Watch said Friday that bombi...