Manila: Police in the northern Philippines have arrested the alleged hitman in last week's killing of a retired but outspoken radio journalist, a national police spokesman said on Sunday.

The gunman was arrested on Friday, six days after he allegedly shot Jose Daguio, 75, Senior Superintendent Agrimero Cruz said, after yet another attack on a journalist in a country considered the most dangerous for the media.

Cruz told DZBB radio that the suspect in custody worked for four brothers allegedly involved in cattle rustling, who were now being sought by police in Kalinga province.

"They will be caught shortly. They have been monitored just moving in the area," Cruz said.

He said murder charges have been filed against all five, after witnesses came out to identify them.

Media groups said Daguio was a long-time commentator for a local radio as well as a columnist for a provincial daily until he retired in the 1980s.

Daguio had continued to be outspoken about alleged irregularities in the province, and Cruz said he had recently named suspects behind cattle rustling in his community.

Daguio was the 140th journalist killed since media freedoms were restored after dictator Ferdinand Marcos was toppled in 1986, a figure that includes 32 journalists slain last year in a massacre blamed on a political warlord.

Daguio was also the first journalist murdered since President Benigno Aquino took office on June 30.

On Friday, another reporter, 48-year-old Miguel Belen of radio station DWEB, in eastern Camarines Sur province, was seriously wounded in an ambush that police said may have been politically motivated.