Rolando "Dodong" Morales of radio station dxMD was shot dead by eight men riding on motorcycles while he was riding home on his motorbike with a companion at around 6 p.m., regional police commander Chief Superintendent Danilo Mangila said.
The gunmen stopped Morales and opened fire with pistols and assault rifles, killing him instantly and wounding his companion, Mangila told reporters.
After Morales fell to the ground, the gunmen shot him again to make sure he was dead. His companion was taken to a nearby hospital, Mangila said.
Morales reportedly suffered 15 gunshot wounds to the head and other parts of the body.
There have been no arrests. An investigation was underway to identify his attackers and their motive.
Morales, 44, had been a vocal critic of illegal drug dealers in the area, Mangila said. He had often accused local government officials of either protecting drug dealers or being involved in the trade themselves, Mangila added.
The gang-style attack happened in Barangay Poblacion, Polomok after Morales Sunday night news commentary program, "Tingog sa Barangay" (Voice of the Village) at the Radio Mindanao Network station based in nearby General Santos City, police said.
It was the third fatal shooting in a week in Polomolok. Two men suspected of being drug pushers were separately killed by unidentified men, police said. Communist and separatist Muslim rebels also have a presence in the area.
Five other journalists have been assassinated in separate attacks this year. In May, a parcel bomb mailed to a journalist killed a 15-year-old boy in Davao City.
The Paris-based watchdog Reporters Without Borders and the New York-based Committee to Protect Journalists has described the Philippines as the worlds "most murderous" country for reporters.
Thirteen journalists were killed in the country last year. Morales was one of 69 journalists slain in the past 19 years since democracy was restored in the country in 1986.
The National Union of Journalists in the Philippines (NUJP) strongly condemned the latest killing.
A week before the ambush, Morales reportedly accused several barangay officials in General Santos City of involvement in summary executions, said NUJP chairwoman Inday Espina-Varona.
"The ambush of Morales highlights the dangerous situation faced by journalists in the Philippines," said Jose Torres Jr., chairman of the NUJPs Committee for the Protection of Journalists (CPJ).
Authorities should immediately probe the incident, the CPJ said while calling on all Filipino journalists to band together against attempts to silence the media.
"Despite the governments claims on upholding press freedom, five journalists have been killed this year," Torres said.
One time, she told The STAR, someone had sent him an ominous phone text message that read: "Mag ingat ka (You better be careful)."
Violeta cried for justice and called on authorities to conduct a "strict" and "thorough" investigation into the murder.
"They mercilessly shot my husband," she bewailed.
Violeta praised her husbands dedication, saying he was a "consistent" crusader against illegal drugs through his radio program.
"Sana makonsensya ang pumatay sa asawa ko. Sana madakip sila para hindi na sila makapatay pa ng ibang tao (I hope my husbands killers will be ridden with guilt. I hope they will be captured so they may not kill some more)," said the teary-eyed Violeta.
Chief Inspector Rex Anongos, the newly installed police chief of Polomolok, said he had no leads on the identity of the eight suspects.
But he assured they would "do our best to identify the killers."
The killers in four motorcycles without license plates, Anongos said. He added the armed men wore helmets and pumped bullets from pistols and M-16 armalite rifles into the victims body.
Residents tried to save the life of Morales, who also worked as an inspector at a pineapple firm, by immediately rushing him to a nearby hospital but attending physicians declared him "dead on arrival."
Morales reportedly had a passenger on the motorbike, a certain Letty Antigua, 44, when the attack occurred. Reports said Antigua was "already out of danger." AFP, Artemio Dumlao, Ramil Bajo, AP, Cesar Ramirez, Edith Regalado