Incendiary Philippine politician Rodrigo Duterte vowed Tuesday a relentless crackdown on crime after securing a landslide presidential victory built on foul-mouthed populist tirades that exposed deep voter anger at the establishment.

The 71-year-old firebrand's main rivals conceded defeat after an unofficial tally showed Duterte had an insurmountable lead in Monday's election of 6.1 million votes, a result that added to howls across the globe for strong, populist leaders.

Duterte, the longtime mayor of the southern city of Davao, captivated Filipinos with vows of brutal but quick solutions to crime and poverty, while offering himself as a decisive strongman capable of resolving a host of other deeply entrenched problems in society.

"It's with humility, extreme humility, that I accept this, the mandate of the people," Duterte told AFP in Davao early on Tuesday morning as the results came in.

"I feel a sense of gratitude to the Filipino people."

In other comments to reporters who had converged on Davao, Duterte offered an olive branch to his rivals following a deeply divisive campaign that had seen President Benigno Aquino brand him a dictator in the making who would bring terror to the nation.

"I want to reach out my hand and let us begin the healing now," said Duterte, whose campaigning style and ability to upend conventional political wisdom have drawn comparisons with US Republican Donald Trump.

However Duterte vowed to push through on the central plank of his campaign platform -- ending crime across the nation within six months and eliminating corruption.

On the campaign trail he had enraged critics but hypnotised fans with profanity-laced promises to kill tens of thousands of criminals, forget human rights laws and pardon himself for mass murder.

- 'Kill threats' -

While avoiding such extreme inflammatory remarks, Duterte said a law-and-order crackdown that particularly targeted drugs would be one of his top priorities when he became president, and he was prepared to kill.

"I will do it (fight drugs), even if they say I am an executioner," said Duterte, who rights groups accuse of running vigilante death squads in Davao that have killed more than 1,000 people.

"Look what I did to Davao. I will not let down the people."

Duterte, who on the campaign trail boasted of being behind the death squads, also had a warning for corrupt police.

"If you are a policeman and stick to your racket, choose: either you kill me or I kill you," he said.

The election commission was not expected to officially proclaim Duterte as the winner of Monday's vote for more than a week.

However it had authorised the PPCRV, a Catholic Church-run poll monitor, to tally the votes, and they showed on Tuesday morning with 91 percent of the total counted that Duterte could not lose.

Duterte had 38.68 percent of the vote, with administration candidate Mar Roxas on 23.32 percent and Senator Grace Poe in third with 21.66 percent, according to PPCRV.

In the Philippines, a winner is decided simply by whoever gets the most votes. The next president will be sworn in on June 30.

Poe, the adopted daughter of movie stars, conceded just after midnight on Tuesday, and Roxas followed just after lunch.

"It is clear Mayor Duterte will be the next president," Roxas told supporters. "I wish you success."

- Gutter talk -

Duterte had during the campaign dominated local media coverage and generated international headlines with relentless gutter talk, including branding the pope a "son of a whore".

He also boasted repeatedly about his Viagra-fuelled affairs.

Duterte caused further disgust in international diplomatic circles with a joke that he wanted to rape a "beautiful" Australian missionary who was killed in a 1989 Philippine prison riot.

Duterte was enraged by the reaction to the rape comments, which included criticism from the US and Australian ambassadors, insisting they were taken out of context.

He said Tuesday it would be up to them to repair relations with him, while also indicating he was prepared to hold direct talks with China over a highly sensitive territorial dispute in the South China Sea.

Analysts said Duterte was expected to moderate his inflammatory comments and he was unlikely to orchestrate his promised massive killing spree against suspected criminals.

"Extrajudicial killings and forgetting human rights, he cannot do that because it will create more instability and chaos, which is what he wants to prevent," Earl Parreno, an analyst from the Manila-based Institute for Political and Economic Reform, told AFP.

"During the campaign he was stage acting, he was exaggerating to get across a message."