Tens of thousands of security forces fanned out across the Philippines Sunday on the eve of national polls, following a bitter and deadly election campaign plagued by rampant vote-buying and intimidation.

Elections are a traditionally volatile time in a nation infamous for lax gun laws and a violent political culture, and they have been inflamed again this year by allegations of massive corruption from the local village to presidential level.

"Vote-buying is everywhere," Commission on Elections (Comelec) commissioner Luie Guia told reporters.

"We are receiving reports that everything is being used to buy votes, not only money. It could be (plastic) basins, groceries."

Such small gifts are an effective, if illegal, way for politicians to win support in a nation where roughly one quarter of its 100 million people live below the poverty line.

To try to check vote buying, the election commission has banned mobile phones in polling places. This is so people cannot photograph their ballots to prove to vote-buyers that they cast their ballots for the right candidates.

At the national level, presidential and vice presidential rivals are also accusing each other of trying to rig the elections.

President Benigno Aquino, who is limited by the constitution to a single term of six years, has warned the favourite to succeed him, Rodrigo Duterte, is a dictator in the making and will bring terror to the nation.

Duterte, mayor of the southern city of Davao, has in turn accused Aquino's administration of planning "massive cheating" to ensure that his preferred successor, former interior secretary Mar Roxas, wins.

Followers of Duterte, who has admitted links to vigilante death squads in Davao that rights groups say have killed more than 1,000 people, have warned of a "revolution" if he loses.

Meanwhile, at least 15 people have died in election-related violence, according to national police statistics.

In the latest suspected case, a grenade blast killed a nine-year-old girl behind the house of a powerful political warlord in the strife-torn province of Maguindanao late on Saturday, said Chief Inspector Jonathan del Rosario.

The girl's death has not yet been included in the tally, although it likely will be, according to del Rosario, spokesman for a police election-monitoring taskforce in Manila.

"This looks like it is election-related but we have a process we have to follow," he told AFP.

Del Rosario said 90 percent of the nation's police force, or about 135,000 officers, were already on election-related duty and had been authorised to carry their assault rifles. He said they were guarding polling and canvassing places and manning road checkpoints.