Philippine President Rodrigo Duterte said on Monday that "plenty will be killed" in his campaign against illegal narcotics trade, which has already led to the death of almost 2,400 people since May.

Duterte is scheduled to meet US President Barack Obama at a regional summit in Laos on Tuesday. Before leaving for Laos, he told Reuters, "Plenty will be killed until the last pusher is out of the streets. Until the (last) drug manufacturer is killed we will continue."

When Duterte was asked about his meeting with US President, he said, "I am a president of a sovereign state and we have long ceased to be a colony."

"Who is he to confront me? As a matter of fact, America has one too many to answer for. Everybody has a terrible record of extrajudicial killings," he added.

The police have claimed that around 900 of those people died in police operations while the rest were "deaths under investigation".