Authorities in the restive southern Philippines defused five roadside bombs near the site in Ampatuan town, in the largely Muslim province of Maguindanao, said provincial police chief Marcelo Pintac. He added that no one was hurt and the blast caused minor damage but tensions were running high.

The bomb was aimed at scaring people away from the commemoration of the 2009 ambush on an election-campaign convoy, he said.

“It was meant to disrupt the activity,” Pintac said of the blast.

About 200 policemen were deployed to secure the massacre site and the immediate vicinity with dozens of people attending the commemoration ceremonies.

According to a military report, two of the homemade bombs were made of 81 mm mortar shells and two-way radios to remotely detonate them. They were found along the national highway near a camp of Muslim rebels.

It wasn’t clear who was responsible for planting the explosives, but about 100 of the 197 people charged are still at large a full two years after the political massacre that became the single worst slaying of journalists in the world.

Leaders of the politically powerful Ampatuan clan and several of their lieutenants have been put on trial over the attack but the proceedings have moved at a snail’s pace, frustrating relatives of the victims.

“We know that it is not easy to get justice. We need to work for it, it is not voluntarily offered or easily obtained,” said Grace Morales, widow of journalist Rosell Morales and sister of another reporter slain in the massacre, Marites Cablitas.

“The families need to act, to remain strong and to continue the fight,” she said in an interview. “It has been two years but we have not yet obtained full justice because not all of them have been detained and sentenced.”

The focus of the trial is Andal Ampatuan Sr., patriarch of the powerful clan in southern Maguindanao province, former governor of an autonomous Muslim region and a political ally of ex-President Gloria Macapagal Arroyo.

Victims’ relatives blame Arroyo for a culture of impunity in the southern Philippines and have filed a lawsuit against her, claiming she could have prevented the killings, although she has condemned the massacre and denied any prior knowledge.

However, Arroyo was arrested just last week on charges of electoral fraud for allegedly instructing Ampatuan and an elections official to rig the results of 2007 congressional polls. She denies any wrongdoing.

Ampatuan is among 96 suspects in custody being tried on murder charges, together with his sons, other relatives and former government-armed militiamen under his wing. They have pleaded not guilty.

Still at large are an additional 100 suspects, including former police, military personnel and civilian militia linked to the Ampatuans, believed to be hiding in Maguindanao and the rest of the restive southern Philippines.

Gunmen allegedly led by Andal Ampatuan Jr., a former town mayor, stopped members of the Mangudadatu clan, the Ampatuans’ political rivals, as they traveled to file for candidacy in regional elections. They were led to a hilltop clearing, gunned down and hastily buried in mass graves alongside their vehicles that were crushed by a backhoe.

“This case underscores what happens when people have full control and absolute power then abuse it,” Interior Secretary Jesse Robredo during a ceremony Wednesday at the massacre site. “They were so brazen and thought nothing could stop them in their time.”

The dead included at least 31 media workers covering the Mangudadatus — making it the worst-ever single massacre of journalists. The charge sheet lists 57 victims but the body of journalist Reynaldo Momay, who was also part of the convoy, was never found.

Still-mourning relatives led by Maguindanao Gov. Esmael Mangudadatu, who lost his wife and sisters in the massacre, lit candles, offered flowers and released doves during the ceremony at the mound where concrete markers bearing the names of dead were erected. He survived an August bomb attack that killed two people in the southern Philippines, where shooting incidents and bomb explosions are common.

Mangudadatu said earlier Wednesday he would scrap a visit to the site in Ampatuan township — named after the powerful clan — after authorities defused at least two bombs nearby. But he later changed his mind and decided to attend.

Robredo said he assured relatives of the victims that the government would do all it can to give them justice and punish all the suspects. But while the government has taken steps to hasten the prosecution, it has suffered delays because of numerous legal tactics by the suspects’ lawyers in a judiciary notorious for a huge number of backlog cases.

“We guaranteed them that under this administration, there would no longer be such warlords because no government will support them,” Robredo said. “As we were traveling back to the airport from the massacre site, I saw along the way that only the police and troops were bearing guns.”

The trial opened last year in a specially built courtroom inside a Manila maximum security prison, where the judge is hearing the case twice a week.

Even from behind bars, the Ampatuans still wield influence and instill fear.

Reynafe Momay-Castillo, the daughter of the undeclared 58th victim, said the suspects’ emissaries were offering money to some relatives in exchange for dropping the case. Amnesty International also has quoted other relatives with similar allegations.

“I don’t feel safe to work,” said Momay-Castillo, a nurse. “We are fighting so many things, not just fighting for justice. We are confronted with the realities of life that go with what happened to our loved ones. The problem is our enemy has so much money.”