COTABATO - A politician whose family was targeted in a southern Philippine massacre that left at least 52 people dead described the attackers as monsters who murdered even his pregnant sister and aunt.

Bulluan Vice Mayor Esmael Mangudadatu also said his wife was sexually assaulted and mutilated before being killed in Monday's slaughter, which he and police alleged was organized by his political rival from another local Muslim clan.

"We can't call him an animal because I have pets and they are tame. No, he is a monster. They are monsters," Mangudadatu told reporters.

He was referring to Andal Ampatuan Jr., a member of President Gloria Arroyo's ruling coalition who police said Wednesday was the top suspect in the massacre.

The killings occurred after about 100 of Ampatuan's gunmen allegedly abducted a convoy of Mangudadatu's aides and relatives, plus a group of journalists.

The victims were abducted as they were travelling in a six-vehicle convoy to an election office where Mangudadatu's wife was to register her husband's candidacy for governor in next year's polls.

Ampatuan, who was also planning to run for governor, carried out the massacre so he would not be challenged for the post, according to Mangudadatu.

The victims were shot at close range a short time after being abducted, then dumped or buried in shallow graves on a remote farming road close to a town bearing the Ampatuan name, police said earlier.

Mangudadatu said Wednesday he had sent his wife, two sisters and aunt, along with other women, to register his nomination because he had been warned that it was too dangerous for him to do it himself.

"We sent women because in the Muslim culture you don't hurt women," he said.

"My youngest sister was five months' pregnant, while my aunt was into her sixth month of pregnancy."

All of his relatives in the convoy were killed, along with two female lawyers and at least 13 journalists, according to police.

Mangudadatu gave a sickening description of his wife's fate.

"My wife's private part was slashed four times, after which they fired a bullet into it," he said.

"They speared both of her eyes, shot both her breasts, cut off her feet, fired into her mouth. I could not begin to describe the manner by which they treated her."

It was not immediately possible to verify Mangudadatu's claims about the mutilation.

Chief Superintendent Josefino Cataluna, regional police chief whose jurisdiction covers Maguindanao, the southern province where the killings took place, declined to comment when asked about Mangudadatu's statements.

However, a mortician's aide at the scene of the mass graves told AFP there on Tuesday that one unidentified woman victim appeared to be pregnant.

Ampatuan Jr. has not commented publicly on the allegations.

His father, the governor of Maguindanao with his own private army who is also a member of the ruling coalition, has promised to cooperate with investigators, according to a presidential adviser.

However, police have not reported making any move to arrest Ampatuan, saying they must first gather all the evidence.