ILIGAN, Philippines: Gunmen killed 13 people in an ambush on a Philippine mayor, police said Friday, in the deadliest of a string of violent incidents that have marred campaigning for May elections.

The attackers opened fire on a truck carrying Mayor Abdulmalik Manamparan and his supporters late Thursday, killing 12 on the spot with another dying later, and leaving 10 wounded, including the mayor, police said.

“They killed my granddaughter,” Manamparan, 62, told AFP from his hospital bed, where he was being treated for a shrapnel wound that grazed his head.

A daughter of the mayor was also among the people killed in the attack on the main southern island of Mindanao, local military commander Colonel Ricardo Jalad said.

Police initially put the death toll at 12, with at least eight wounded, but Senior Superintendent Gerardo Rosales, chief of the Lanao del Norte province, later updated the figures on television.

He blamed the attack on long-running clan disputes by Muslim families in the country’s troubled south.

President Benigno Aquino’s spokeswoman Abigail Valte said the authorities were attempting to establish the identities and motives of the attackers.

“We strongly condemn this act of violence,” she told reporters in Manila.

“We appeal to the supporters of the different candidates to keep calm and continue to campaign for their particular candidates.”

The ambush on a remote mountain road near Nunungan town, unleashed as the mayor and his party travelled home from a campaign event, was the latest episode of political violence in a country that will hold mid-term elections on May 13.

An updated running police tally now lists a total of 46 deaths from at least 48 violent incidents reported since the start of the campaign in February.

In November 2009, members of a powerful clan on Mindanao abducted and murdered 58 people including relatives of a local rival who was planning to challenge the clan leader in gubernatorial elections the following year.

Manamparan is the mayor of the mainly Muslim town of Nunungan. He is standing for the lower post of vice-mayor. His son and namesake, who is running for mayor, was not among the ambush casualties.

The family is running against candidates backed by President Benigno Aquino’s Liberal Party.

The mayor told AFP he had a good idea who was responsible for the attack, but declined to discuss his suspicions.

Rosales said police investigators are checking the involvement of certain clans which had had previous scraps with the Manamparan family.

“They (survivors) identified the attackers last night, they gave us names... They told us it was a family feud,” Rosales told reporters.

Colonel Jalad said the ambush was the first big incident of political violence in Nunungan in the past year.

However, he said Nunungan and nearby predominantly Muslim areas of Mindanao were blighted by occasional killings linked to decades-old clan wars.

Mindanao is also wracked by insurgencies waged by Muslim and communist rebels, and officials say that some of this year’s election violence has been committed by communist guerrillas extorting money from candidates.

New People’s Army rebels ambushed Ruth Guingona, the 78-year-old mayor of the southern city of Gingoog on April 21, killing two of her aides and wounding her and two policemen.

More than 18,000 posts are at stake in the balloting, from town mayors and governors to members of parliament.

Two election campaigners in a province near Manila were killed and another wounded in an ambush Thursday, while a district official was killed on the same day in a bomb blast elsewhere on Mindanao, police said.