Bangkok: A five-year-old girl has become the youngest victim of tough-talking Philippines President Rodrigo Duterte's "war on drugs" that has left more than 1900 people dead in seven weeks.

Danica May died from a gunshot wound to the head after unidentified gunmen opened fire on her family as they sat down to lunch in their home in Dagupan, a city of 170,000 north of Manila.

The killing came as president Duterte shrugged off criticism of his campaign from the United States, United Nations, the Catholic Church and human rights groups, declaring "this fight against drugs will continue until the last day of my term".

Little Danica's grandfather, Maximo Garcia, who she was living with after her 29-year-old mother separated from her husband, learnt last week that he was on a list of alleged drug suspects that somebody had given to local police.