Roger Mariano's final minutes on the air were true to his reputation as the premier radio crusader in the northernmost Philippines. He was especially animated about alleged graft at the local electric utility. And when he finished his nightly show on Saturday, July 31, he confided to a colleague that he had uncovered records proving corruption.

"It will be a big bomb for my Monday show," Mariano said, according to an account by the station manager.

Then he slung a bag with the document over his shoulder, his colleagues recalled, and got on his motorcycle for the 10-mile drive home. An hour later, his body was found along a dark stretch of a rural road, shot about 10 times in the back and several times more in the head.

Mariano was the third Philippine journalist murdered this year. Since then, three more have been slain in separate incidents, making the Philippines the most dangerous country for journalists in the world outside of Iraq, according to the New York-based Committee to Protect Journalists.

In a country where newspaper reporters and radio broadcasters have long risked harm to tackle sensitive issues, 55 members of the media have been murdered since the reintroduction of democracy and press freedom following the ouster of President Ferdinand Marcos in 1986, according to the National Union of Journalists of the Philippines.

Most of the targeted journalists have been broadcasters. In the provinces, radio is king. It reaches into the most remote villages and poorest neighborhoods and, unlike newspapers, is free.

But the prominence this affords correspondents is no guarantee of safety. When journalists report about controversial issues, they can find themselves entangled in a web of overlapping political, business and criminal interests with little protection from local police.

"The culture of impunity in Philippines sets it apart from other places," said Abi Wright of the Committee to Protect Journalists. "There is no chance of retribution if you act against a journalist."

With the recent killings, President Gloria Macapagal Arroyo has announced rewards for the capture of the killers. The national police have set up a task force to investigate the cases.

Not a single case involving the murder of journalists since 1986 has yielded a conviction. Media advocates attribute this to the power of those who order the killings and their ability to hide hired killers in other parts of the country. This track record, in turn, explains the increasing frequency of these murders, advocates say.

"The fact that no one is convicted for killing journalists really encourages people to attack media practitioners," said Inday Espina-Varona, chairwoman of National Union of Journalists of the Philippines.

In some cases, journalists in the provinces have apparently been attacked after becoming involved in questionable business enterprises or taking money from local powerbrokers to disparage their rivals, advocates said.

But they stressed that in at least three cases this year -- the deaths of Mariano, radio and newspaper correspondent Arnel Manalo in Batangas and radio commentator Eliseo Binoya near General Santos City -- the murders were connected to their legitimate work as journalists.

Mariano, 44, was a short, slight man with a shadow of a mustache. He was quiet, even taciturn, when out with friends or home with his wife and eight children. But behind the large, black microphone at DZJC Aksyon Radyo in Laoag, he railed and harangued against crime and corruption.

"It was exciting work but most of all he wanted to educate and reach the minds of the people about what's happening in our province and around the world," said Temy Simeon, a fellow broadcaster who had been Mariano's best friend since they both went to work at another Laoag radio station 14 years ago.

Mariano started at DZJC early last year, and he had become popular, said station manager Diomedes V. Lorenzo.

By early July, his show, "Roger Mariano in Action," had grown from a Sunday show, to a daily 90-minute program. But his friends and colleagues were already starting to worry that his relentless criticism of crime and corruption in Ilocos Norte province was becoming too risky.

Lorenzo, the station manager, suggested to Mariano that he temper his commentaries, especially about illegal gambling.

"I warned him to lay low," Lorenzo recalled. "But he said it's our role to let the public know." Lorenzo answered that he was not trying to silence Mariano. "I warned him there are syndicates, and we don't have any defense against these syndicates," Lorenzo recounted.

Mariano's wife, Alma, said she had begged him to quit the radio station and look for work in Manila. "He wouldn't listen. He said he was just doing his job," she recalled. Alma grew so scared in the weeks before his death that she stopped listening to his broadcasts.

During July, Mariano focused on the widely used illegal numbers racket, known as jueteng, which some journalists claim flourishes under the protection of local authorities.

He also began raising allegations about the Ilocos Norte Electric Cooperative, a government-regulated utility. According to a colleague, Mariano had obtained a copy of a secret memorandum of understanding for the utility to purchase power from a private electricity generator.

Following the July 31 broadcast, Mariano was fired up when he set off for home shortly after 7 p.m., colleagues recounted. He drove out of the provincial capital, Laoag, crossing a bridge over the broad Pagsanjan River to the town of San Nicolas on the southern bank. As usual, he stopped at the public market, tucked beside a Spanish colonial stone church, to buy food for his family's dinner, picking up a bag of anchovies, according to police accounts.

Then he continued on under a moonless sky. After two miles, the homes of San Nicolas gave way to an open, desolate stretch of country road.

Suddenly, a van with three armed assailants raced alongside Mariano's motorcycle, police said based on a crime scene investigation and witness testimony. The gunmen opened fire with at least one M-16 assault rifle and a carbine, striking Mariano in the back as he fled on his bike. His body came to rest beneath an acacia tree on the right side of the road. The motorcycle careered into an adjacent rice paddy.

At least one of the gunmen got out of the van and yanked off Mariano's helmet, police reported. Then the assailant shot him repeatedly in the right temple to make sure he was dead. His shoulder bag and cellular telephone were taken.

Col. Rolando Rabara, director of Ilocos Norte provincial police, said the gunmen were hired killers. He said investigators have several suspects and have concluded that the murder was almost certainly linked to Mariano's prominent role as a radio journalist.

"Here, if you are a broadcaster, if you are a commentator, it is normal to have enemies, especially if it is government officials you are criticizing," he said.

Rabara said the murder was most likely connected to Mariano's investigative reporting into the electric utility, though police are also examining a link to his reports about illegal gambling.

"It would be just to silence him," he said.

A team of national, provincial and local police has been established to probe Mariano's murder, Rabara said, but the effort is hamstrung by the fear of witnesses, the same problem confronting the investigations of journalist murders elsewhere in the country. "We find a hard time to get witnesses. We don't have solid evidence," he said.

But local journalists, who declined to be named, said they worry the crime will never be solved because the local police are too close to powerful figures behind the murder.

"If the brutal killing of Roger Mariano is not solved, this will embolden more killings of media people," Lorenzo warned.

Already, the murder has had a chilling effect. Mariano's on-air colleague, Lolita Reyes, has toned down the aggressive commentaries on her show "Lolita Rides Again," according to Lorenzo. Other journalists said broadcasters and newspaper reporters in Laoag are more cautious about what they say, especially concerning the electric utility and gambling rackets.

"They are afraid they could take the next bullet," said local newspaper reporter Teddy P. Molina.

A journalist covers his face during a protest march last month in Quezon City outside Manila. More than 50 journalists have been killed since 1986.