Duterte: We'll not stop til all surrendered or put behind bars or below the ground, if they so wish

Mr Duterte promised instead to protect police and soldiers who kill suspects.

"I will answer for the deed. If policemen are involved in encounters (with drug suspects), don't investigate it," he said.

Tens of thousands of Filipinos have surrendered to police as panic has spread over the killings, further crowding jails where in some inmates are jammed body-body on concrete floors.

Mr Duterte promised when he was sworn into office in early June that his anti-crime battle will be "relentless and sustained" and urged police to "seize the moment."

But he has not so far put forward any policy proposals on criminal justice or crime control, saying the killings are proof of the success of his campaign.

During Mr Duterte's 22 years as mayor of the southern city of Davao death squads killed hundreds of suspected criminals, drug dealers and street children as young as 14, according to an investigation by Human Rights Watch.

No charges were ever laid over the killings.

Mr Duterte said last month he is not afraid of going to jail, as he was aged 71, but added that as president he has immunity from prosecution.

Sixteen million Filipinos voted for Mr Duterte after he campaigned vowing to kill suspected drug dealers and other criminals and that fish in Manila Bay would grow fat on the bodies.