People cast their votes during the presidential election at a polling precinct in Quezon City, suburban Manila on May 9, 2022. (TED ALJIBE / AFP)

MANILA - Voting in the Philippines continued on Monday to elect their next president and some 18,000 other officials of all levels of government, despite the eruption of violence in the southern Philippines that killed three and injured nine.

A total of 37,211 polling centers across the country opened at 6 am local time (2200 GMT Sunday) for over 65.7 million eligible voters and will close at 7 pm local time (1100 GMT).

Also to be elected are the vice president, 12 senators, more than 300 members of the House of Representatives, and over 17,000 local officials.

Also to be elected are the vice president, 12 senators, more than 300 members of the House of Representatives, and over 17,000 local officials

Presidential candidate frontrunner and former Senator Ferdinand Marcos Jr., 64, who is the son of former President Ferdinand Marcos, cast his vote in the morning at the Mariano Marcos Memorial Elementary School in Batac City, Ilocos Norte province, north of main Luzon island.

His main rival and incumbent Vice President Maria Leonor Robredo, 57, cast the ballot in her hometown of Naga City of Bicol region, south of Luzon island. She expressed hope that voting and counting will be peaceful and credible.

Davao City Mayor Sara Duterte-Carpio, 43, the daughter of outgoing President Rodrigo Duterte and frontrunner of the vice-presidential race, cast her ballot inside a high school in her hometown of Davao City on Mindanao island.

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As the the voting continued, violence erupted mainly in the southern Philippines, leaving three dead and nine injured.

Interior Secretary Eduardo Ano said three people were killed and one injured in a shooting incident near a polling center in Maguindanao province in the southern Philippines on Monday morning.

He said the attackers opened fire at the members of village peacekeepers helping in the voting process in Buluan town around 7:25 am local time (2325 GMT).

The Commission on Elections also reported another strafing incident on Monday morning in Sumisip town in Basilan province in the southern Philippines. The poll body said there were no casualties in the attack.

People look for their names on voter registration lists during the presidential election at a polling precinct in Quezon City, suburban Manila on May 9, 2022. (TED ALJIBE / AFP)

Police reported an improvised explosive device went off around 9:40 a.m. local time (0140 GMT) near a polling center in Kabacan town in Cotabato province. There were no casualties in the blast that delayed the voting process.

Earlier Monday, police also reported at least eight persons were injured in grenade explosions in Maguindanao province on Sunday night, the eve of the voting.

Police said the explosions hit Datu Unsay town, and another one hit nearby Shariff Aguak town.

No group has claimed responsibility for the explosions. Police are looking into the attacks in the areas tagged as "hot spots." Authorities said the eruption of violence in these areas did not disrupt the voting process.

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The government has put 45,000 soldiers and 60,000 police officers in charge of maintaining order during the elections. An additional 12,000 police force is on stand-by if violence breaks out in some areas.

The Commission on Election has tagged 104 municipalities and 14 cities as "hot spots" due to armed groups and intense political rivalry, which could trigger election violence.