MANILA (Reuters) - The Philippines on Monday began a manual recount of votes in a vice presidential election after the son and namesake of former dictator Ferdinand Marcos contested the outcome, while the incumbent assured supporters her win was not in doubt.

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Ferdinand Marcos Jr, a former senator popularly known as Bongbong, is furious about having lost to Leni Robredo by about 260,000 votes in a May 2016 election he says was marred by massive cheating.

Many political commentators believe Marcos has ambitions to become president one day, and wanted to use the vice presidency as a stepping stone. Opinion polls had shown him the clear leader ahead of the vote, which is separate from that for the presidency.

The recount, ordered by the Supreme Court, began with Marcos questioning the condition of some ballots from the town of Bato in Robredo’s home province of Camarines Sur.

“In four precincts in the town of Bato, all ballots are wet and thus useless,” he told reporters. Alluding to foul play, he added that the ballots seemed to be “only recently wet”.

Audit logs for most of the precincts were missing, he said, and he had seen a ballot box with a hole sealed with a masking tape.

“We have nothing to fear because the truth is what we are fighting for,” Robredo, a one-term congresswoman before the 2016 election, said in a speech after a mass service organized by her supporters in the largely Roman Catholic country.

Robredo, who hails from a decades-old political clique that opposes Duterte and helped oust Marcos in 1986, had lodged a counter protest, questioning results in about 8,000 voting precincts.

Although he was not his running mate, Marcos is on good terms with President Rodrigo Duterte, who has made numerous concessions to the Marcos family.

He has constantly praised the leadership of the late dictator, fuelling concern among some Filipinos that he might cling on to power.

Ferdinand Marcos declared martial law in 1972 and held power for 14 years until his removal in a bloodless, military-backed “People Power” uprising.