Bangkok: Philippines President Rodrigo Duterte could face international criminal charges as the death count in his relentless war on drugs tops almost 2000, human rights advocates say.

Comments by the tough-talking former provincial mayor such as "all of you are into drugs, you sons of bitches … I will kill you" could be used as evidence to prosecute him, they say.

Sam Zarifi from the International Commission of Jurists (ICJ) says it is likely that as the killings continue lawyers will gather evidence to initiate legal proceedings against Mr Duterte like 9541 victims of the late Philippines dictator Ferdinand Marcos did in the United States in the 1990s.

In 1995 a US court awarded the victims $US1.9 billion after finding that Marcos, who died in exile in 1989, was responsible for massive human rights abuses, including torture, murder and "disappearances of fellow Filipinos".