A Filipino lawyer filed a complaint against President Rodrigo Duterte and other officials before the International Criminal Court (ICC) on Monday, accusing them of crimes against humanity in a nationwide anti-drugs crackdown.

In the 77-page complaint, Attorney Jude Sabio said Duterte "repeatedly, unchangingly and continuously" committed crimes against humanity and that under him, killing drug suspects and other criminals has become "best practice".

Sabio is the lawyer of Edgar Matobato, a man who has testified in the Senate that he was part of a hit squad that operated on Duterte's orders when he was still Davao city mayor.

It is the first publicly known communication to the ICC against Duterte, and is based on the testimony of Matobato and retired policeman Arturo Lascanas, statements from rights groups and media reports, including a Reuters series on the killings.

It was filed the same week that Duterte will chair the 30th Association of Southeast Asian Nations (ASEAN) Summit, to be held in the Philippine International Convention Center in Pasay City from April 26 to 29.