MANILA, Philippines — The Philippine national police chief warned Monday that law enforcers will be going after more drug lords following a raid that left 15 people dead, including a city mayor who was among politicians President Rodrigo Duterte had publicly linked to illegal drugs.

Police Director General Ronald dela Rosa said authorities are building up cases against more illegal drug operators included on Duterte’s list, warning that the police will enforce the law “without fear or favor.”

Officers were about to serve warrants early Sunday to Ozamiz Mayor Reynaldo Parojinog Sr. to search his houses for the suspected presence of unlicensed firearms when gunmen opened fire on the police, sparking clashes that killed the mayor and at least 14 other people, said Ozamiz police chief Jovie Espenido.

Espenido, who oversaw the simultaneous, post-midnight raids on Parojinog’s residence and three other houses, described the mayor as a “high-value target on illegal drugs.” Policemen were approaching the mayor’s house when his bodyguards opened fire and hit a police car and wounded an officer, sparking a firefight amid a power outage, he said.

Eight people were arrested, including two of Parojinog’s children — Ozamiz Vice Mayor Nova Princess Parojinog-Echavez and her brother Reynaldo Parojinog Jr., officials said. The siblings were flown Monday to the national police headquarters in Manila.

Dela Rosa denied allegations of a rubout, saying the operation in Ozamiz resulted in deaths because the police were met with armed resistance.

Asked by reporters who the next drug lords to be targets of police operations will be, dela Rosa said, “There are many of them because there are many in the president’s list.”

“If they are not doing anything bad, they should have no fear, but if it is validated that they continue to be involved in drugs then they have to prepare themselves,” dela Rosa said. “The (police) will implement the law without fear or favor.”

Also on Monday, Justice Secretary Vitaliano Aguirre II ordered the immigration bureau to be on the lookout for seven suspected illegal drug operators, including at least two publicly linked by Duterte to the narcotics trade. Anyone who is the subject of an immigration lookout bulletin needs to get permission from the justice secretary to leave the country.