A Philippine mayor on President Rodrigo Duterte's list of allegedly narcotics-linked officials was shot dead Monday by a "sniper" in a broad daylight attack at a town ceremony, police said.

Antonio Halili was hit in the chest by a single shot fired from a distance, unleashing chaotic scenes during the weekly flag raising ceremony at the town hall in Tanauan, south of Manila.

In the moments that followed, terrified onlookers screamed and the mayor's security details opened fire, video of the scene showed.

However, the shooter managed to escape and Halili was pronounced dead at hospital.