President Rodrigo Duterte and Agnes Callamard. Photo Composite

MANILA - The Philippines on Friday said it would complain to the United Nations after one of its human rights investigators failed to notify the government of a visit to Manila on Friday, which it said was a "clear signal" she was not interested in an objective view.

Agnes Callamard, the U.N. Special Rapporteur on extrajudicial killings, gave a speech at a policy forum at a university on Friday, and said she was not in the Philippines in an official capacity and would not carry out any research.

The Philippine government has directed its representatives to the UN to raise Callamard's unannounced visit to their counterparts, said Presidential spokesman Ernesto Abella.

"This is a matter we have asked our representatives at the United Nations to take up with their United Nations counterparts and it is something our delegation in Geneva will certainly be raising during their current visit," Abella said in a statement.

He said Callamard arrived "in a manner that circumvents all recognized United Nations protocols for such visits."

"We are disappointed that, in not contacting our government in advance of this visit, she has sent a clear signal that she is not interested in getting an objective perspective," Abella said in a statement.

Callamard, a French humanitarian, has been vocal about allegations of systematic summary executions in the Philippines as part of President Rodrigo Duterte's war on drugs, which has killed thousands of people.

The Duterte administration invited her last year to investigate the allegations but declined as she found that government's conditions - including that she publicly debate Duterte - were far from agreeable.

Callamard said a debate would contravene U.N. protocols, and instead proposed a joint news conference.

"The fact that Dr. Callamard did not respond to our invitation showed that she would not be approaching her review of allegations concerning our country objectively or comprehensively," Abella said.

Callamard mentioned different approaches to tackling illicit drugs in general at Friday's forum, although not specifically the Philippines.

She said the U.N. General Assembly had recognized last year that drug wards did more harm than good.

"Badly thought out, ill-conceived drug policies not only fail to address substantively drug dependency, drug-related criminality, and the drug trade, they add more problems," she told a forum hosted by the Free Legal Assistance Group.

She later told reporters she had no ulterior motive for visiting the Philippines. "It's only for the purpose of academic conference," she said.

The United Nations and the Philippines have different accounts of Callamard's intent to investigate drugs-related killings, which activists attribute to police.

More than 7,000 killings have been recorded since President Duterte took office and initiated his anti-drug war, but the government has maintained that less than half were killed in legitimate police operations.

On Thursday, Duterte again rejected those allegations.

Authorities say police are only responsible for deaths that were in self-defense during anti-drugs operations, while the rest were carried out by vigilantes or rival gangs. -- with reports from Dharel Placido, ABS-CBN News