Phillipines President Rodrigo Duterte
Phillipines President Rodrigo DuterteReuters

President Rodrigo Duterte threatened on Sunday to withdraw the Philippines from the United Nations, as he launched another profanity-laced tirade against the organisation for criticising his bloody war on crime.

More than 1,500 people have been killed since Duterte took office and immediately began his law-and-order crackdown, according to police statistics, triggering fierce criticism from the UN and rights groups.

Duterte, a lawyer famous for an acid tongue who has repeatedly told the UN not to interfere, on Sunday stepped up his rhetoric against the organisation.

"Maybe we'll just have to decide to separate from the United Nations. If you are that disrespectful, son of a *****, then I will just leave you," Duterte said in a press conference in his home city of Davao that started about 1:00 am.

Duterte said he may even try to set up a rival international organisation.

"I would invite everybody. I would invite maybe China, the African (nations)," he said.

The UN's special rapporteur on summary executions, Agnes Callamard, last week said Duterte's promise of immunity and bounties to security forces who killed drug suspects violated international law.

UN Secretary-General Ban Ki-moon in June also strongly criticised Duterte, who during the election campaign promised to kill 100,000 people and dump so many bodies in Manila Bay that the fish would grow fat from feeding on them.

"I unequivocally condemn his apparent endorsement of extrajudicial killings, which is illegal and a breach of fundamental rights and freedoms," Ban said.

Duterte frequently peppers his public comments with swear words -- he has also called Pope Francis and the US ambassador to Manila sons of ***** - and days after his election win used typical language to criticise the UN.

"**** you, UN, you can't even solve the Middle East carnage... couldn't even lift a finger in Africa," he said then.

Tirade against UN

Duterte lashed out in a similar fashion on Sunday, accusing the "stupid" UN of not doing anything in Middle East hotspots Syria and Iraq.

Duterte referenced a haunting photo taken last week of a little Syrian boy, who was pictured sitting in an ambulance dazed and covered in blood after an air strike, as evidence of the UN's ineffectiveness.

"Is that stupid body complaining about the stench there of death. Look at the iconic boy taken out of the rubble. When he was made to sit in the ambulance, and we saw it. So what's the difference?"

And Duterte asked why police killings in the United States were not attracting the same kind of criticism as the Philippines.

"What do you think the Americans did to the black people there? Is that not rubbing off also? And (critics) say what?"

Duterte also accused the UN of doing nothing for the Philippines - ignoring its poverty reduction programmes and enormous help following typhoons and other natural disasters.

On the day he was sworn into office, Duterte called for people in slums to kill neighbours whom they believed were drug addicts, repeating a campaign line.

His aides have since said such comments are merely hyperbole and not meant to be taken literally.

However nearly 900 people have been murdered by unknown people during Duterte's time in power, with police killing another 665 alleged drug suspects, according to the national police chief.

The killings represent a massive increase on crime deaths since Duterte took office.

Duterte has repeatedly insisted police have only killed in self defence, while maintaining the other deaths are due to drug syndicates killing each other.

Duterte and his aides have given conflicting positions on whether they would allow UN experts to come to the Philippines to investigate allegations government security forces are carrying out extrajudicial killings.

On Sunday, he contradicted his spokesman's comments from the previous day and challenged them to come.

"You law experts of the United Nations, come here and face me and make the accusations," he said.

On Wednesday last week he said if an investigator came to the Philippines, "I'd like to box him in the head".