MANILA - Police are investigating 899 killings nearly two months into President Rodrigo Duterte's war on drugs, the head of he Philippine National Police said Thursday.

Scores of drug suspects have been killed in police operations and suspected vigilante attacks since Duterte assumed office on June 30, raising alarm among lawmakers and human rights groups.

The police data, which was submitted to a Senate investigation on Thursday, was based on a tally from July 1 to August 15, Director General Ronald dela Rosa said.

''We cannot really attribute this to vigilante killings. These are found dead bodies under investigation,'' dela Rosa said in response to a question from Senator Grace Poe.

The ABS-CBN Investigative and Research Group counted 1,081 drug-related deaths from May 10, when Duterte's election mandate became clear, to August 17.

Of this figure, 653 people were killed during police operations, while 335 were killed by unidentified assailants. At least 93 bodies were discovered away from the crime scene.

Poe, who lost to Duterte in the May 9 vote, said it is important to make sure that the rights of individuals are protected and rule of law is maintained as law enforcers crack down on drug rings.