US Secy of State meets Philippines' Duterte despite rights concerns

US Secretary of State Rex Tillerson brushed aside questions about the Philippines' deadly drug war on Monday as he received a warm welcome from President Rodrigo Duterte.

Duterte's 13-month-old administration has launched a brutal crackdown on drugs that has claimed thousands of lives and led to warnings by rights groups that he may be overseeing a crime against humanity.

But Washington fears offending its long-time ally could push it into the arms of US rival China, and it is backing Philippine troops as they battle to recapture part of a southern region occupied by militants aligned to the Islamic State group.

When Duterte welcomed Tillerson to his palace on Monday the pair ignored reporters' questions about human rights, and afterwards the Philippine leader insisted the topic had not come up at the talks.

"They did not," Duterte replied when asked if US officials raised human rights during the discussions.

Last week, before Tillerson travelled to Manila to attend meetings with fellow foreign ministers at a regional diplomatic and security forum, US officials said he would raise the issue of the drug war.

But, just before the meeting, Tillerson denied there was any tension between Washington's support for the fight against the Islamic State group and concerns about the alleged extra- judicial killings.

Tillerson described the crisis in the southern Philippine city of Marawi as a "tragic situation" and said US forces were providing surveillance aircraft and important advice for the Philippines forces in the battle there.

"Bringing our knowledge in how to deal with this enemy in other parts of the world is useful to them, and I think that is also in our security interests as well," he told US journalists at his hotel.

"I see no conflict at all in our helping them with that situation, and our views on other human rights concerns that we have in how they carry out their counter-narcotics activities."

Duterte easily won presidential elections last year after promising an unprecedented war on drugs in which tens of thousands of people would be killed.

Since he took office in the middle of last year, police have confirmed killing more than 3,400 people in anti-drug operations.

More than 2,000 other people have been killed in drug- related crimes and thousands more murdered in unexplained circumstances, according to police data.

Rights groups say many of those victims have been killed by government-backed vigilantes, and Duterte has himself boasted that he would be "happy to slaughter" three million drug addicts.

Former US president Barack Obama was among the many international critics of the drug war.

Duterte, who frequently uses coarse language against his critics, responded by branding Obama a "son of a whore" last year.

Duterte also used the criticism as justification for loosening the Philippines' decades-long alliance with the United States in favour of warmer ties with China.