MANILA - A former mayor, tagged in the government's list of "narco-politicians", and his brother were gunned down on Friday (Jan 4), just hours after President Rodrigo Duterte threatened to slit the throats of "big-time" drug dealers.

Mr Talib Abo, former mayor of Parang town, Maguindanao province, in the volatile southern part of the Philippines, died after a shoot-out with anti-drug enforcers who were attempting to execute a search warrant just past midnight on Friday, according to police reports.

His brother Bobby was killed in a separate raid at around the same time.

"They resisted and shot it out with our teams," Mr Juvenal Azurin, head of the Philippine Drug Enforcement Agency in the area, told the online news site Rappler.

Mr Abo is the sixth mayor killed in the government's controversial drug war, which has left over 5,000 dead since Mr Duterte came to power in June 2016.

In 2006, Mr Duterte accused Mr Abo of smuggling 3.5 kilos of crystal meth, known locally as "shabu", to Davao city using an ambulance. Mr Duterte was at the time mayor of Davao city.

Mr Duterte said Mr Abo and his wife headed a "vast network" of drug dealers in the central and southern parts of the war-torn southern Philippine island of Mindanao.

Mr Abo and his brother were killed soon after Mr Duterte said he would personally slit the throats of drug lords in front of human rights activists.

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"If you are a big time player, I will not forgive you. I will slit your throat in front of human rights (activists) . I don't care. I'm telling you not to do that to my country. I will get you. So I could not be more clear," he said at a birthday party of one of his top political supporters on Thursday evening.

Mr Abo was the second senior politician in Maguindanao to be killed in Mr Duterte's war on drugs

In October 2016, Mr Samsudin Dimaukom, mayor of Saudi Ampatuan town, in Mindanao, and 10 of his men were gunned down in a clash with anti-narcotics officers at a checkpoint.

Both were on the list of public officials Mr Duterte accused of being involved in the narcotics trade.