A member of a powerful political clan on Tuesday pleaded not guilty to murder charges in the Philippines' worst election massacre of 57 people, including journalists and members of a rival's family.

Andal Ampatuan Jr., a town mayor in southern Maguindanao province where his family ruled unopposed for years, has been initially charged with 41 counts of murder in the Nov. 23 attack on an election caravan in the volatile southern Philippines.

Sporting a designer watch and a necklace with an "A," Ampatuan stood emotionless beside his lawyer in front of Regional Trial Court Judge Jocelyn Solis Reyes as a court staffer read the charges accusing him of "conspiring, confederating and mutually helping" others in the gruesome murders. He is the only suspect charged with murder in the killings thus far.

Prosecutors said there was "evident premeditation" in the killings, characterized by the use of "superior strength, treachery and cruelty."

Prosecutors said they have witnesses who will testify that Ampatuan led more than 100 government-armed militiamen and police in stopping the caravan at a security checkpoint outside Ampatuan township, then forcing the victims at gunpoint to a hilltop clearing where they were gunned down and buried in mass graves.

Among those killed were at least 30 journalists and their staff in what is considered the world's deadliest single attack on media workers. The carnage has sparked international outrage, prompting President Gloria Macapagal Arroyo to briefly impose martial law in Maguindanao to crack down on the powerful Ampatuan clan, a key political ally, and its private army.

Ampatuan's father, the former provincial governor who heads the clan, and several other close relatives also have been accused of involvement in the killings but have yet to be indicted. They too have denied any role in the massacre.

The victims included the family and supporters of the Ampatuans' election rival, Esmael Mangudadatu, who sent his wife, sisters and other female relatives to file his candidacy papers hoping they would not be harmed. Mangudadatu said Ampatuan threatened to kill him if he ran for governor in national elections in May.

Prosecutors presented Ricardo Diaz of the National Bureau of Investigation as their first witness. He said he received autopsy reports, statements from witnesses, pictures and video footage of bodies and the crime scene.

Ampatuan's lawyer, Sigfrid Fortun, won a ruling from the judge disallowing as evidence a flash disk that purportedly contained video and pictures of the victims on grounds that Diaz did not personally record them.

Prosecutors said they will present investigators who recorded the images at the next hearing scheduled for Jan. 13.