MANILA - Senator Panfilo ''Ping'' Lacson on Monday challenged the Philippine National Police (PNP) to stop the growing number of drug related vigilante killings.

Lacson, who served as PNP chief from 1999 to 2001, said policemen should dispel notions that they support vigilante groups and cannot suppress crime by themselves.

Vigilante groups, inupakan ni Sen Lacson; PNP hinamon na pigilan ang mga ito | via @dzmmPatrol44 pic.twitter.com/FakwyGgYzc

— DZMM TeleRadyo (@DZMMTeleRadyo) August 15, 2016

"The war against illegal drugs is rightly in our manifesto, but do not allow vigilantes to act as lynch mobs with no regard for the law to blindside you," he said.

"Let the public know of your unflinching commitment to fight these vigilantes, lest they suspect that the police itself is the sponsor of these vigilante killings, not to mention the perception that you cannot do it alone and within the established norms of law enforcement."

Lacson earlier urged PNP to solve the drug suspects' summary killings, reportedly perpetrated by vigilante groups.

A tally by the ABS-CBN Investigative and Research Group shows that 1,000 drug suspects have already been killed between May 10 and August 12.

Of this number, 598 were killed in police operations while 311 were murdered by unidentified assailants and 91 were found away from the crime scene.

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The Senate committee on justice will conduct a hearing on the spate of extra-judicial killings on August 22 and 23.

Lacson advised PNP officials who will attend the investigation to "be careful in answering questions but they should not deviate from the truth."