U.S. President Donald Trump said on Monday he had a "great relationship" with his Philippine counterpart, Rodrigo Duterte, while a White House official said human rights got only a brief mention when the two met on the sidelines of an Asian summit.

A spokesman for Duterte said there was no mention at all of human rights or extra-judicial killings during their conversation.

The meeting between the two presidents was one of the most anticipated at the summit of East and Southeast Asian leaders in Manila, with human rights groups pressing Trump to take a tough line on Duterte over his bloody war on drugs, in which thousands of people have been killed.

"The conversation focused on IS, illegal drugs, and trade," said White House spokeswoman Sarah Sanders.

"Human rights briefly came up in the context of the Philippines' fight against illegal drugs."

Harry Roque, Duterte's spokesman, told a news conference that the Philippine president had explained his anti-drugs policy at length to Trump, who "seemed to be appreciative of his efforts".

"There was no mention of human rights, no mention of extra-legal killings," he said.

More than 3,900 people have been killed in a war on drugs that Duterte declared when he took office last year. His government says the police acted in self-defence, but critics say executions are taking place with no accountability.

"We are your ally. We are an important ally," Duterte told Trump at the beginning of their talks, according to reporters allowed into the meeting room.

Trump replied: "We've had a great relationship. This has been very successful. And the Asean (Association of South East Asian Nations) conference has been handled beautifully by the president in the Philippines."

Duterte, who has been called the "Trump of the East" for his brash style and provocative language, said last week he would tell the U.S. president to "lay off" if he were to raise accusations of rights violations.

Love song

Trump was criticised in May for praising Duterte during a phone call for the "great job" he was doing to counter illegal narcotics.

The US and Philippines, a former U.S. colony, have been strategic allies since World War Two. But their relations have been strained by anti-US outbursts from Duterte and his enthusiasm for better ties with Russia and China.

However, Duterte clearly appears to be getting on better with Trump than he did with his predecessor, Barack Obama. Trump and Duterte seem to have warmed to each other after meeting for the first time on Saturday at an Asia-Pacific Economic Cooperation (Apec) group meeting in Vietnam.

On Sunday, Duterte crooned hit Filipino love song "Ikaw" (You) at a gala dinner for summit leaders in Manila, saying it was on "the orders" of Trump.

One of the song's verses, translated from Filipino, begins: "You are the light in my world, a half of this heart of mine".

"Ladies and gentlemen, I sang uninvited, upon the orders of the commander-in-chief of the United States," Duterte said later, according to the ABS-CBN news channel.

Roque described the relationship between Trump and Duterte as "warm, friendly and candid".

"It's very apparent that both of them have a person who they consider as not a best friend," he added.

"They have similar feelings towards former US president Barack Obama."

Duterte's anger was unleashed last year when Obama raised concerns about possible human rights abuses in the war on drugs. Duterte said Obama could "go to hell" and called him a "son of a bitch".

- Reuters