Philippines drug trade

It is the first such admission he has made since becoming president in June, but echoes comments he made in 2015.

He ran the southern city for two decades, earning a reputation for cutting crime, and criticism for allegedly supporting death squads.

Mr Duterte was speaking to business leaders at the presidential palace on Monday, before an overseas trip.

Duterte said Saturday he did not realize the severity of the problem until he became president. He's been accused of ordering or encouraging hundreds of killings of drug dealers and users since taking office in June.

"But the problem is ... I cannot kill them all ... even if I wanted to," he told reporters. "I did not have any idea that there were hundreds of thousands of people already in the drug business and what makes it worse is that they are operated now by people in government -- especially those elected positions."

Death squad