Jose Velasco reached into a drawer of his desk and pulled out a stack of color photographs. Better than any statistics, they illustrate why this southern city, the country's third largest, has acquired a reputation as the Philippines' "murder capital."

As manager of Davao's DXMF radio station, Velasco has taken it upon himself to document the mounting murder rate here that has accompanied intensified warfare between guerrillas of the Communist New People's Army and the armed forces of President Ferdinand Marcos. So far this year he has counted more than 530 killings in Davao City, an area 50 miles long and 30 miles wide with a population of about 1 million.

When he hears that a body has been discovered, he grabs his camera and rushes to the scene. His photographs of 41 victims show that these are not ordinary slayings. They are pictures of an underground war of uncommon brutality and violence that seems to have no legal remedy.

Here are headless bodies and victims of horrible beatings and mutilations. Here are young men with hands and feet bound behind their backs before execution. Here are middle-class victims slain on downtown streets, as well as poor slum-dwellers fished out of this port city's waters.

Among the dead are a pregnant woman and her mother-in-law, shot by unidentified gunmen for unknown reasons. Another photograph shows the body of a man gunned down inside a clinic, a blood pressure gauge still wrapped around his arm. Then there is a well-dressed bank employe shot in the head on his way to his office, his wife and daughter kneeling in the street in a pool of blood and weeping over his body.

One of the radio station's reporters, Chito Herbolingo, used to help keep track of the killings until one day in April. Arriving at a site where three youths had been killed the night before, he found that one of the bodies was that of his 17-year-old brother. The youth, allegedly killed by drunken government militiamen, was the 50th victim that month, and the last one Herbolingo counted.

Practically all of Davao's murder cases are unsolved, lawyers said, largely because no witnesses are willing to testify.

Asked if he has ever covered a murder trial during his eight-year tenure here, station manager Velasco stroked his silver beard and asked, "A murder trial? In Davao City? I don't remember one."

Lawyers believe most of the killings are the work of either the military or guerrilla assassination squads called "sparrow" units. But others are thought to be committed by extortionists or persons seeking revenge in personal disputes. Often it is difficult to tell. Usually the killings are attributed officially only to "unidentified gunmen."

Among the latest victims was a local radio reporter, Armando Pingoy, 45, who was shot by unknown assassins while he was moonlighting as a plainclothes security guard. He was the first reporter to be killed following a claim by the military to have recovered a rebel "death list" of nine Davao broadcast and print journalists marked for assassination. However, Pingoy's name was not on the list, and the New People's Army has dismissed the document as a military fabrication.

Nevertheless, it is clear that journalism in the Philippines has become a hazardous calling. According to the National Press Club of the Philippines, at least 16 journalists have been killed since the middle of last year. By comparison, the press club lists six journalists killed between 1975 and mid-1984.

One of this year's victims was an anticommunist radio commentator, Charles Aberilla, gunned down by suspected guerrilla hit men who burst into his announcer's booth in Iligan City, on northern Mindanao, while he was on the air. Listeners heard the fatal gunshots, followed by his dying moans.

Military men are considered suspects in several other cases, and some of the killings are attributed to journalists' involvement in love affairs or businesses, not to mention rackets.

ERLENE DANGOY, 16, is obviously a troubled girl. It shows in her dark eyes, which at times appear near tears and at other times smolder with anger as she tells her story.

She was arrested March 19 in the Panacan barrio north of Davao shortly after the murder of a neighbor, Erlinda Batulan, 31, who allegedly was killed by Communist assassins for being a military informer. The slain woman's husband pointed out Dangoy to authorities as having been involved in the killing.

She denies any involvement in the murder or in the New People's Army, and she claims not to know why she was accused.

Upon her arrest, Dangoy said in an interview, she was taken to the Sasa police station near the city. There, she said, guards stripped her naked and administered electric shocks to her fingers and nipples to extract a confession and information implicating other suspects. She said guards also placed bullets between her fingers and squeezed them, and kicked her in the face.

Several days later, she said, she was taken to the Philippine Constabulary headquarters in Davao City, where she was put in a small guardhouse near the entrance. There, she said, a Philippine Constabulary guard, Alex Capuyan, raped her on three consecutive nights from March 25 through March 27, and two other men sexually molested her. She said guards warned her that if she complained, she and her parents would be killed.

Despite the threats, Dangoy decided to press charges against Capuyan. While still in detention, she wrote to the Davao Lady Lawyers' Association to appeal for help and express her anguish and shame.

In April, Dangoy said, she was cleared of murder and subversion charges, but she was not released until July 16. In the meantime, she said, officers told her the subversion charges would be dismissed if she would drop the rape case.

According to senior military officers, however, Capuyan is being held on the rape charge and the case will be pursued.

Dangoy's friends said she recently underwent an illegal abortion and has difficulty sleeping.

Asked what she intends to do now, she looked resolute. "I plan to push through with the case no matter what happens," she replied quietly. Afterward, she said, she will leave the Davao area "for my safety."