The Philippines will look into thousands of killings in President Rodrigo Duterte's war on drugs, its justice minister said on Wednesday, after a review of a sample of cases indicated foul play in dozens of deadly police operations.

Menardo Guevarra said his Department of Justice (DOJ) would expand its review to the more than 6,000 killings during police operations, after which many officers were cleared of wrongdoing in internal police investigations.