KORONADAL, Philippines (AP) — Philippine anti-narcotics officers gunned down a town mayor and nine of his men in a clash Friday in one of the bloodiest operations since President Rodrigo Duterte launched a crackdown on illegal drugs.

Mayor Samsudin Dimaukom of Datu Saudi Ampatuan town, who was killed with the nine others, has been publicly named by Duterte among many politicians he accused of involvement in illegal drugs as part of a shame campaign.

In August, Duterte read out the names of more than 150 officials allegedly linked to illegal drugs. He ordered them to surrender to authorities immediately or be hunted down. The mayor had turned himself in to police and denied he was involved in the illegal drug trade. He had told the media that he was fighting illegal drugs himself and supported Duterte's crackdown.

"It was a legitimate anti-drug operation but the subjects opened fire on our troops," regional police official Superintendent Romeo Galgo Jr. told reporters.

They were killed before dawn when they opened fire from three cars on officers at a checkpoint in Makilala town in North Cotabato province, another officer, Superintendent Bernard Tayong, said.

Ahead of the deadly firefight, police received information that Dimaukom's group was planning to transport a "huge" amount of methamphetamine — a prohibited and extremely addictive stimulant drug locally known as shabu — from Davao city, Duterte's hometown, to Maguindanao province, where Datu Saudi Ampatuan town is located.

Police estimate more than 3,600 suspected drug dealers and addicts have been killed since Duterte took office on June 30. The crackdown has drawn international concern over extrajudicial killings, but Duterte has repeatedly dismissed criticism and vowed to keep his election promise to rid the country of drugs.

Associated Press writer Jim Gomez in Manila, Philippines, contributed to this report.