Philippine President Rodrigo Duterte will host world leaders in Manila from Sunday, hoping their presence will quieten international criticism over his deadly drugs war, which rights groups say may be a crime against humanity.

Duterte goes into the event appearing confident that even his most outrageous remarks and actions will be ignored, having boasted in the lead-up he once stabbed someone to death, while at the same time proposing to host a global human rights summit.

US President Donald Trump will be among leaders from 19 countries, plus the heads of the United Nations and European Union, coming for the talks, which will begin with a banquet on Sunday night followed by summits on Monday and Tuesday.

But rights groups have expressed alarm and disappointment that Trump and most others are likely to endorse or stay silent over Duterte's violent rule, which has seen thousands of people killed.

"Duterte will enjoy the gift of tacit silence from East Asian leaders on his murderous drug war during the upcoming summit," Human Rights Watch deputy Asia director Phelim Kine told AFP.

"We can expect East Asian leaders to exercise a diplomatic blind eye to the killings of thousands of Filipinos over the past 16 months as part of Duterte’s drug war."

Duterte won last year's presidential elections after promising to eradicate illegal drugs with an unprecedented crackdown that would see up to 100,000 people killed.

Since Duterte took office, police have reported killing 3,967 people in the crackdown.

Another 2,290 people have been murdered in drug-related crimes, while thousands of other deaths remain unsolved, according to government data.

Many Filipinos back Duterte, believing he is taking necessary measures to fight crime.

But rights groups warn he may be orchestrating a crime against humanity.

Amnesty International accuses police of shooting dead defenceless people and paying assassins to murder addicts.

Rights groups say police are following Duterte's incitements to kill, citing comments of his such as he would be "happy to slaughter" three million addicts.

Domestic opponents have appealed to the International Criminal Court to investigate, pointing to the jailing of opponents, a compliant congress and intimidated judiciary as reasons to step in.

- A 'great job' -

But the ICC has yet to respond and, despite some vocal critics in the West, Duterte goes into the Manila summits full of confidence that Trump and the others will effectively endorse his rule by not speaking against the killings.

In Vietnam on Thursday on the sidelines of an Asia-Pacific economic summit, Duterte boasted that when he was 16 he stabbed to death someone for looking at him the wrong way.

He then offered to host a global summit on human rights, but insisted that the alleged crimes of the United States, France and other nations also be investigated.

Duterte, 72, last year branded then-US president Barack Obama a "son of a whore" for criticising the drug war.

But Trump and Duterte have expressed mutual admiration for other. Trump told Duterte in a telephone call in April that he was doing a "great job" with his campaign against drugs.

They are expected to hold one-on-one talks on Monday and, if Trump does not bring up any human rights concerns, Duterte is widely expected to trumpet the meeting as an endorsement.

"We will be extremely disappointed if Trump does not raise it," Amnesty's Philippine director, Jose Noel Olano, told reporters on Saturday.

Duterte is hosting the two days of summits as the rotating chair of the 10-member Association of Southeast Asian Nations (ASEAN).

Duterte can expect blanket support from his ASEAN colleagues, many of whom are also shadowed by human rights controversies.

"From the Rohingya crisis in Myanmar, to a sweeping crackdown on all forms of dissent in Cambodia to the thousands killed in Philippines, human rights are under siege across Southeast Asia," Rachel Chhoa-Howard, a Philippine researcher with Amnesty, told AFP.

The premiers of China and Russia, two other important Duterte backers, will also be in Manila.

Japanese Prime Minister Shinzo Abe is another key backer of Duterte, with the pair having established a warm relationship.

Source: AFP