MANILA - Police pulled bullet-ridden bodies from shallow graves on Tuesday as troops hunted down the gunmen who massacred at least 23 people in one of the country's most brutal explosions of political violence.

Authorities warned the death toll would climb higher as they sought to deal with the fall-out of Monday's events in which one political clan in Maguindanao is alleged to have tried to wipe out its rivals.

"It's a big area where these bodies were found. They are finding a couple of bodies every a couple of hours or so," Interior Secretary Ronaldo Puno said as he described a farming area covered in hastily dug graves.

Puno said the extra bodies being recovered were on top of the 23 accounted for in the official death toll, but he would not speculate on how many people in total had been murdered.

"They are still looking for some missing persons. A number of other bodies were found. I can't really reveal the details now. It's a large number," Puno told the ABS-CBN.

A report by ABS-CBN Cotabato News anchor Lerio Bompat said local authorities are using a backhoe to excavate the murder site amid reports that some of the victims were buried there with their vehicle.

She said the bodies of most of the victims, which include mediamen, have not been moved while investigation is ongoing. "The victims are outside of the vehicles, lying on the grass. Some of the bodies were mutilated. Wala silang kalaban-laban," she told ANC.

Political violence is common in the Philippines -- where more than one million unlicensed guns proliferate -- and dozens of people are murdered each election season. But the scale of Monday's massacre, as well as the targeting of apparently unrelated people, has shocked the country.

Fourteen of the victims were women and some of them were journalists with no apparent links to the clan war, the police and military said.

Authorities previously said more than 40 people had been abducted on Monday by gunmen linked to Maguindanao governor Andal Ampatuan, the head of a Muslim clan who is part of President Gloria Arroyo's ruling coalition.

The abducted group was made up of relatives and associates of Esmael Mangudadatu, the head of a rival Muslim clan in Maguindanao, plus a group of journalists, the military and police said.

The group was travelling in a convoy to accompany or report on Mangudadatu's wife as she went to an electoral office to register her husband to run for governor against Ampatuan's son in next year's national polls.

Military spokesman Lieutenant-Colonel Romeo Brawner said the Ampatuans and their associates were believed to have been responsible for the massacre.

"The suspects are bodyguards of Ampatuan, local police aides and certain lawless elements," Brawner said.

As thousands of soldiers fanned out across the Ampatuans' stronghold in search of the gunmen on Tuesday, sickening details of the massacre emerged.

The military said about 100 armed men stopped the convoy of vehicles on a remote section of highway near the town of Ampatuan, which bears the same name as the political kingpin.

Police said the bodies of the victims were found a few kilometers (miles) away, with a bulldozer apparently used to dig the graves still on the scene.

Police said 15 of the victims appeared to have been shot inside their vehicles while one was believed to have been cut down by gunfire while fleeing.

"All were shot at close range," said one of the investigators on the scene, Chief Superintendent Felicisimo Khu.

Asked about the allegations by some of the victims' relatives that the murdered women were also raped, Khu said: "We cannot confirm that although all the women had their pants unzipped."

The Ampatuan clan are the long-time political kingpins of Maguindanao, a mainly Muslim section of Mindanao island which has been wracked by a Muslim separatist rebellion for decades.

The Ampatuan patriarch, Andal Ampatuan Snr, has been governor for the past nine years and wants his son and namesake to succeed him.

The Ampatuan clan has been important in delivering votes to Arroyo's ruling Lakas Kampi-CMD coalition in recent elections. The Ampatuan father is the provincial chair of the coalition in Maguindanao.

Amid this backdrop, Interior Secretary Puno vowed the government would be impartial as it pursued justice.

"I just want to assure everybody that we are doing everything necessary here, that there will be no sacred cows," Puno told ABS-CBN.

"This is going to be a direct investigation of the crimes that have been committed and we are going to hold the persons responsible for this." With Agence France-Presse