Candidates linked to Philippine ex-leader Rodrigo Duterte appear to have won election victories, including Duterte himself, despite him being detained for alleged crimes against humanity.

Former Philippine President Rodrigo Duterte has secured a landslide victory in the Davao City mayoral race, even as he remains in detention at the International Criminal Court (ICC) in The Hague on charges related to his controversial anti-drug campaign.

With 80% of votes counted in an unofficial tally, Duterte, who was brought to The Hague in March over his bloody "war on drugs" that killed thousands of people, was winning the Davao mayoral contest with eight times more votes than his nearest rival.