Three journalists in the Philippines have been shot dead just days apart, press groups said Tuesday (Sep 1), as they warned of further media bloodshed without serious government action.

The nation of 100 million people has long been one of the world's most dangerous places for journalists, with powerful figures able to kill critics in the knowledge they will rarely face punishment.

"We call on President Benigno Aquino to give top priority to swiftly resolving these egregious cases," said Shawn Crispin, senior Southeast Asia representative for the Committee to Protect Journalists.

"Until Aquino demonstrates his government is serious about ending the onslaught, the killings will inevitably continue."

Police and the CPJ said the latest victim was radio commentator Cosme Maestrado, 46, shot dead in front of a public market in the southern port city of Ozamiz on August 27. Before Maestrado, radio reporter Teodoro Escanilla, 57, was shot inside his home in a fishing town in rural Sorsogon province on August 19, according to local police and the CPJ.

A day earlier, newspaper reporter Gregory Ybanez, 67, was gunned down in front of his house in Tagum city, a banana-growing centre in the south, where he also headed the local press association, police said.

The Philippines is infamous for a "culture of impunity", where the rich and powerful can literally get away with murder by taking advantage of corrupt police and judicial figures.

The latest killings bring to 29 the number of journalists murdered since Aquino assumed office in 2010, according to the National Union of Journalists of the Philippines. Out of the 168 cases of media killings since the restoration of democracy in 1986, only 13 suspects had been convicted of murder and sent to jail, NUJP director Sonny Fernandez said.

"The government has failed to stop the killings. There should be convictions, that's the only way they can prove that they're serious," Fernandez told AFP.

Presidential spokesman Herminio Coloma said it was "inappropriate" to blame the murders on impunity. "Government is taking necessary action to identify and arrest suspects and bring them before the bar of justice," Coloma said.

National police spokesman Chief Superintendent Wilben Mayor told AFP he could not immediately provide statistics on arrests or charges filed in cases regarding media killings.

The world's deadliest attack against journalists took place in the Philippines in 2009, when 32 journalists were among 58 people killed by a warlord clan intent on stopping a rival's election challenge. The chief justice said recently she expected verdicts against more than 100 people on trial for the massacre would be announced early next year.