Rodrigo Duterte, a brash crime-fighting mayor nicknamed “the Punisher”, has claimed victory as the next Philippine president after building an insurmountable lead in election returns.

The firebrand figure, who has vowed to order mass killings of criminals and feed their bodies to the fish of Manila Bay, secured the presidency with a crushing victory.

"It's with humility, extreme humility, that I accept this, the mandate of the people," Mr Duterte told AFP as the results came in, adding his law and order platform was the key to his success.

"What I can promise you is that I will do my very best not just in my waking hours but even in my sleep."

The country faced immediate prospects of political upheaval as a close aide said the new president would press for a “major re-writing” of the constitution to introduce a parliamentary system.

Mr Duterte had vowed to push for the introduction of a federal government to break Manila’s dominance and share resources with the provinces.

And in a society famed for its love of fiestas and karaoke, there could be other major changes on the way.

Peter Lavina, his spokesman, said that a late night drinking ban and curfew on unaccompanied minors on the streets after 10pm could be extended across the nation from his from Davao City base.