MANILA A crude bomb exploded on Wednesday near a memorial for 58 victims of the Philippines' worst election-related violence hours before the start of a rally to commemorate the attack two years ago, police said.
Two bombs were found and safely disarmed near the massacre site in Ampatuan town, in the southern largely Muslim province of Maguindanao, said provincial police chief Marcelo Pintac, adding that no one was hurt and the blast caused minor damage.
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.
The other two devices, one made out of an artillery shell and the other from a mortar bomb, were left where they would be easily found, he said.
Among those who attended the ceremony was provincial governor Esmael Mangudadatu, who lost his wife and several relatives in the attack. Thirty-three media people were also killed.
The convoy was traveling on a mountain road to witness Mangudadatu's wife filing her husband's papers for a May 2010 election when gunmen struck. Victims were taken down a dirt road and shot and buried in mass graves. Some were buried in their vehicles.
Mangudadatu was standing against a powerful political clan run by the Ampatuan family.
The government has filed murder charges against 196 people, including former provincial governor Andal Ampatuan and his four sons. About 80 people have been arrested but only 64 are on trial, including the primary suspect who is one of the sons, Andal "Unsay" Ampatuan.
The U.S. ambassador to the Philippines, Harry Thomas, said people around the world were closely watching the legal proceedings into the "appalling act of violence."
"The prosecution of this case is seen ... as demonstrative of the Philippines' commitment to upholding the rule of law and protecting human rights," Thomas said in a statement.
Those attending the commemoration lit candles and released white balloons and doves. They called on the government to take steps to resolve the case quickly.
The Ampatuans ruled Maguindanao for nearly a decade and were supporters of former President Gloria Macapagal Arroyo.
Friday, Arroyo and the elder Andal Ampatuan were charged with electoral sabotage in connection with accusations of rigging 2007 Senate elections in Maguindanao to favor Arroyo's allies. Both denied the accusations and moved, through their lawyers, to dismiss the cases.
Arroyo, a two-term president from 2001 to 2010, was arrested last Friday on charges of electoral fraud.
(Reporting By Manuel Mogato; Editing by Rosemarie Francisco)