The police chief of the Philippines on Wednesday stood by the head of a secretive unit behind dozens of killings in the country's war on drugs, saying officers fired only in self-defense and the death toll reflected the danger and the scale of the narcotics problem.

National Police Chief Ronald dela Rosa was responding to a Reuters Special Report that spent four months examining killings by one group of policemen from or near Davao City, the hometown of Philippine President Rodrigo Duterte.

Dela Rosa said police district 6 in Quezon City had Metro Manila's most serious drug problem and he personally sent squad commander Lito Patay there because he was a "very professional" and "very dedicated" officer capable of dealing with it.