Newly inaugurated Philippine President Rodrigo Duterte has urged communist rebels to start killing drug traffickers and people to kill addicts, adding another layer to a controversial war on crime in which he has warned thousands will die.

Key points: Rodrigo Duterte invites communists to "use kangaroo courts to kill criminals"

Rodrigo Duterte invites communists to "use kangaroo courts to kill criminals" The 4,000-strong communist army is known for assassinating civilians

The 4,000-strong communist army is known for assassinating civilians Mr Duterte also calls for drug addicts to be killed

Mr Duterte also calls for drug addicts to be killed A bullet-riddled body is found, marking the first extrajudicial killing of Mr Duterte's presidency

The communists' armed wing, the 4,000-strong New People's Army, is known for assassinating civilians deemed to have committed so-called crimes against the people — however its courts and summary executions are illegal.

"Drugs have reached the hinterlands ... what if you use your kangaroo courts to kill them to speed up the solution to our problem," Mr Duterte, a lawyer and former city prosecutor, said in a speech before the military's top brass in Manila.

In a late-night speech on Thursday to a slum community in the capital attended by only a few journalists, Mr Duterte also called on ordinary Filipinos to kill drug addicts, which is also illegal.

"If you know of any addicts, go ahead and kill them yourself," he told a crowd of about 500 people.

Mr Duterte also vowed to kill drug traffickers, using foul language he promised in recent weeks to "tone down" as president.

"These sons of whores are destroying our children," the 71-year-old said.

"I warn you, don't go into that, even if you're a policeman, because I will really kill you."

'Duterte must break rhetoric as president'

A former mayor of the southern city of Davao, Mr Duterte had alternately denied and confirmed running death squads there that summarily executed suspected criminals.

Mr Duterte won May's election in a landslide after a campaign dominated by his pledge to end crime within six months, promising to do so by unleashing security forces with shoot-to-kill orders.

In his inauguration speech on Thursday, Mr Duterte insisted his adherence to the rule of law was "uncompromising", apparently seeking to assuage concerns from human rights groups that he planned to orchestrate mass extrajudicial killings.

Amnesty International said it was encouraged by Mr Duterte's inauguration pledge to honour the country's obligations under international law.

"But now he is in power, he needs to lend substance to those words and break with his earlier rhetoric," Rafendi Djamin, the rights group's director for South-East Asia and the Pacific said in a statement.

Before dawn on Friday a bullet-riddled body was found in a Manila slum with a sign on it that read: "I am a Chinese drug lord," local police said.

The murder bore all the hallmarks of an extrajudicial killing, which would make it the first of Mr Duterte's presidency.

Sorry, this video has expired Beverley O'Connor speaks to Chay Hofilena from Philippines social news network Rappler.

AFP