More people have been killed “outside of police operations” than during law enforcement campaigns in President Rodrigo Duterte’s anti-illegal drug drive since July 1, the head of the Philippine National Police (PNP) told a Senate hearing on Monday.

PNP Director General Ronald dela Rosa said the total number of fatalities from July 1 to August 22, he said 712 were killed during police operations, while 1,067 were "outside of police operation" and "under investigation.

"If any policeman is found violating law on self-defense, he will be investigated, prosecuted and punished," Dela Rosa said.

Of the 1,067 deaths, 268 are before the prosecutor’s office, he said.

Some quarters have been criticizing the reported increasing number of extrajudicial killings amid Duterte's all-out war against illegal drugs.

Senator Leila de Lima, chairperson of the committee on justice and human rights, presented 12 witnesses on eight cases involving 11 deaths of drug suspects either killed in the police operation or by alleged vigilante groups. Only two have testified.

A Pasay police officer said two policemen allegedly involved in killing two drug suspects on July 6 were charged Monday morning with murder before the City Prosecutors' Office.