The accused include the so-called "Godfather" of the clan. Hundreds of police and security agents have been detained and reports say the entire police force of the province will be replaced.
Women victims were reported to have been mutilated.
Bai Genalin Mangudadatu, wife of Buluan Vice-Mayor Esmael Mangudadatu, suffered 17 gunshot wounds and several "incised wounds," according to a medical report of the National Bureau of Investigation. But the NBI reportedly found no sign of rape among the 15 female victims it had examined.
Genalin had been on her way to file her husband's certificate of candidacy for Maguindanao governor when gunmen blocked her convoy and killed her and at least 56 others on November 23.
Maguindanao Governor Andal Ampatuan Sr is one of eight members of his clan indicted by prosecutors probing the massacre.
He has been described as the "Godfather" of the political clan favoured by President Gloria Arroyo.
The prosecutors have charged him with multiple murder, destruction of property and robbery.
Ampatuan Sr's son, Mayor Andal Ampatuan Jr, is already in jail on charges of masterminding the election-related killings and on 25 counts of murder.
Another of Ampatuan Sr's sons, Governor Zaldy Ampatuan of the Autonomous Region of Muslim Mindanao, has also been asked by Interior Secretary Ronaldo Puno to answer within five days allegations that he had failed "to protect the civil, human and political rights" of the victims.
An Al Jazeera report described the powerful Ampatuan clan as "political untouchables".
A congressman accused the government on Friday of being the biggest arms supplier of Filipino warlords after the discovery of a large arms cache near the mansion of Governor Zaldy Ampatuan Jr on Thursday.
"The arms cache found near the Ampatuans' mansion confirms that the government, particularly the AFP (Armed Forces of the Philippines), is the biggest arms supplier of the country's warlords," Bayan Muna Representative Teodoro Casiño said in a text message.
“This bloodbath is beyond human understanding,” says a journalist from the nearby city of Koronadal. He told Reporters Sans Frontières: “I have lost 12 of my colleagues in this massacre.”
Nonoy Espina of the National Union of Journalists of the Philippines (NUJP), who is in Mindanao, told Reporters Sans Frontières before the latest arrests of the clan leaders: "The government is not doing enough to arrest those responsible."
Eight of the journalists have now been buried and media people will stage a protest rally at Mendiola, Manila, on Wednesday, December 9.
Meanwhile, an international emergency mission led by the International Federation of Journalists (IFJ) has arrived in the Philippines to support local journalists and the National Union of Journalists of the Philippines (NUJP) in the wake of the massacre.
The delegation comprises representatives from leading journalists' rights and press freedom organisations including the IFJ, the Southeast Asia Press Alliance (SEAPA), the Committee for the Protection of Journalists (CPJ), the Alliance of Independent Journalists (AJI), the Media Entertainment & Arts Alliance MEAA - Australia), the Thai Journalists' Association (TJA), International News Safety Institute (INSI), International Media Support (IMS), the Institute for Studies on the Free Flow of Information (ISAI) and Union Network International (UNI).
- Contacts: Rorie Fajardo of PHRRP: (0905) 315 4986 and firstname.lastname@example.org
Sonny Fernandez and Alwyn Alburo of NUJP: (0918) 9213712 and
Trina Federis of CEGP: (0910) 4803098 and email@example.com
Sweet Cawicaan of CCJD: 376-5550 and (0927) 9165160
- Background on the massacre is posted on the Reporters Sans Frontières website.