The son of late Philippines dictator Ferdinand Marcos on Wednesday claimed victory in the presidential election, vowing to be a leader "for all Filipinos", his spokesman said.

With an initial count almost complete, Ferdinand Marcos Jr, popularly known as "Bongbong", has secured over 56 percent of the vote and more than double the tally of his nearest rival, liberal Leni Robredo.

In his first press conference, Marcos said that 31 million Filipinos had "voted for unity," even as he waits for the vote counting to finish.

His win is an astonishing reversal in the fortunes of the Marcos family, who have gone from the presidential palace to pariahs and back again in the space of a few decades.

"To the world, he says: Judge me not by my ancestors, but by my actions," spokesman Vic Rodriguez said in a statement.

Voters had been predicted to back Marcos by a landslide in Monday's election, after relentless online whitewashing of the family's past, the backing of powerful political dynasties and public disenchantment with post-dictatorship governments.

The son of the late Philippines dictator Ferdinand Marcos has claimed victory in the presidential election
The son of the late Philippines dictator Ferdinand Marcos has claimed victory in the presidential election AFP / MIKHAEL FLORES

For years, pro-Marcos accounts have flooded social media, leaving many young Filipinos believing his father's rule was a golden period of peace and prosperity.

In reality, Marcos senior left the Philippines bankrupt and impoverished, and killed, tortured and jailed tens of thousands of opponents during his corrupt dictatorship.

Hours after his thumping victory, Marcos Jr visited his father's grave at the national heroes' cemetery in Manila.

Photos posted on official Marcos social media accounts on Wednesday showed him standing before the tomb with his head slightly bowed and covering his eyes with his right hand, as if crying.

For years pro-Marcos accounts have flooded social media, leaving many young Facebook-educated Filipinos believing his father's rule was a golden period of peace and prosperity
For years pro-Marcos accounts have flooded social media, leaving many young Facebook-educated Filipinos believing his father's rule was a golden period of peace and prosperity AFP / CHAIDEER MAHYUDDIN

Marcos vowed to "hit the ground running" when he takes office on June 30, with the economy, prices, jobs and education to be his government's priorities.

"I know that the counting is not over, it is not yet official, but I'm always guided and always look to the fact that 31 million of our countrymen voted for unity," Marcos told reporters at his campaign headquarters in Manila.

Marcos refused to take questions at the end of the press conference, which lasted less than five minutes.

He is waiting for all the votes to be counted before he declares victory, Rodriguez told reporters earlier.

The president-elect was greeted by a crush of supporters as he arrived at the headquarters before fronting the media.

The crowd erupted in cheers when Marcos grabbed a cardboard sign from a fan that read: "Thank you 31 million."

"I am so happy, so overwhelmed," said Joseph Bugayong, a 30-year-old gardener standing outside the building.

Supporters of Philippine presidential candidate Ferdinand Marcos Jr celebrate outside his campaign headquarters
Supporters of Philippine presidential candidate Ferdinand Marcos Jr celebrate outside his campaign headquarters AFP / JAM STA ROSA

"I saw him in person and even shook his hand. My wait was worth it."

The United States said it would seek close security ties with the Philippines under a Marcos government, but made clear it would raise human rights.

US Secretary of State Antony Blinken sent a congratulatory message to Marcos, saying Washington looks forward to working with him to "strengthen the enduring alliance" between their countries.

"As friends, partners and allies, we will continue to collaborate closely with the Philippines to promote respect for human rights and to advance a free and open, connected, prosperous, secure and resilient Indo-Pacific region," Blinken said.

"Our expectation is we'll be able to continue to work closely," said Kurt Campbell, the top White House official on Asia, acknowledging that there may be some "challenges in the communication.

The Marcos family's astounding journey from ignominy back to political favour has overshadowed questions about what Marcos Jr's administration would do.

There were few hints on the campaign trail after Marcos snubbed televised debates and largely avoided media interviews as he sought to avoid own goals.

Rights groups, Catholic church leaders and political analysts fear the huge win could embolden Marcos to rule with a heavy fist and push through constitutional changes that could entrench his rule.

His running mate Sara Duterte, the daughter of the outgoing president, also won the vice presidency, which is elected separately, in a landslide.

Their success at the ballot box means the two offspring of authoritarian leaders will hold the highest elected positions for the next six years.

In his first cabinet appointment, Marcos said Duterte would serve as education secretary.

The overwhelming win has devastated Robredo's supporters, who saw the election as a make-or-break moment for the country's fragile democracy.

Many of them went door to door across the vast archipelago in a months-long effort to convince voters to support the liberal candidate for the top job.

Robredo, a 57-year-old lawyer and the current vice president, has admitted "clear disappointment" about the result but vowed to continue the fight against poor governance.

Marcos will have to contend with this opposition that could congeal into a potent pro-democracy movement.

"I think they could still be in a position to check the worst instincts of the incoming Marcos and Duterte administration," said political analyst Richard Heydarian.