MANILA - The mayor of a small Philippine town, the main suspect in the November massacre of 57 people in the country's troubled south, pleaded not guilty to murder charges on Tuesday.

Datu Andal Ampatuan Jr, wearing handcuffs and flanked by armed security officials, sat quietly and looked bored as a court employee read 41 murder charges against him at a clubhouse turned into a courtroom inside Manila's main police camp.

State prosecutors are readying 16 more murder cases against Ampatuan Jr. to cover each of the 57 people killed, including 30 journalists, some of whom were found in shallow, hastily dug graves at a hilly area in southern Maguindanao province.

Most of the victims were on their way to an election office to witness the filing of nomination papers for a member of the Ampatuans' rival political clan when about 100 armed men attacked their convoy.

The killings raised fears next May's national elections would be bloody, particularly the contest for provincial posts.

Days after the massacre, President Gloria Macapagal Arroyo imposed martial law in Maguindanao province to disband the Ampatuan's private army and arrest the clan's patriarch, his brother and three sons, suspected to have had a hand in the killings.

All five are currently under military and police custody on the southern Mindanao island.

On Tuesday, Arroyo appointed a retired judge to head an independent commission tasked to dismantle private armies controlled by dozens of political warlords across the country and reduce election-related violence.

Arroyo gave the commission authority to use the military, police and other agencies to disarm and disband an estimated 132 private armed groups.

Troops have so far seized more than 1,100 assault rifles, mortars, machineguns, bazookas, armoured vehicles and more than half a million rounds of assorted bullets from the Ampatuan clan in the government crackdown on the family's private army since last month.
The military has initiated an inquiry on the Ampatuan's arsenal after 10 percent of the munitions were found to be owned by the government and most of the assault rifles were imported from the United States and Israel.

(Reporting by Manny Mogato; Editing by Rosemarie Francisco and Jeremy Laurence)