At least 57 people were killed in the stunning massacre of journalists, civilians and relatives of politicians in the volatile southern Philippines as more bodies were unearthed from a mass grave, military and police officials said.

Ltcol Romeo Brawner, the chief military spokesman, said 11 bodies were discovered as rescuers continued to dig the hillside grave in Saniag village, Amputuan town of Maguindanao province on Wednesday.

Twenty-two victims were female and about 20 were journalists, officials said, but there is no confirmed report of survivors.

The victims were on a convoy through Amputuan town Monday to register Esmail Mangudadatu as governor candidate for next year's provincial election. They were stopped by around 100 militiamen and were herded away from the main road before being shot in front, at close range, by M-16 rifles. Machete wounds were also found on victims' bodies.

National Police Spokesman Chief Superintendent Leonardo Espina Wednesday said initial reports indicated the influential Maguindanao Governor Andal Ampatuan Sr. and his son -- Unsay town mayor Andal Ampatuan Jr. -- are behind the massacre.

Mangudadatu is said to have irked the Amputuans by trying to compete with Andal Ampatuan Jr. for the governor's post in next year's election.

But no arrests were made as the police are still gathering evidence. President Gloria Macapagal-Arroyo imposed the emergency rule in the area on Tuesday to give security forces a freer hand to arrest and detain suspects.

However, the military authorities ordered the disbandment of about 240 para-military men belonging to the Amputuan family. They were initially accused of being involved in the killing, Brawner said.

"Nobody is above the law. The long arm of the law somehow will catch up with them," Executive Secretary Eduardo Ermita told a news briefing on Wednesday. He urged the Ampatuans and those who " may feel alluded" to come out and present themselves to the authorities.

Political violence is not uncommon in the Philippines, especially in Muslim Mindanao, a region plagued by decades of insurgency battles and flooded with loose arms.

But the indiscriminate killing of women, working journalists, and civilian supporters shocked the nation and the international community.

Presidential Adviser on Mindanao Affairs Jesus Dureza said " specific actions" can be expected in 24 hours but he did not say if these actions involve arrests.