MANILA, Philippines — The United States on Tuesday expressed concern over the spate of extrajudicial killings and detentions in the Philippines, which under President Rodrigo Duterte has undertaken a crackdown on drugs and criminality.

Elizabeth Trudeau, director of the United States Department of State's press office, said Washington urges the Philippines to follow legal and human rights principles in its efforts against illegal drugs.

"We are concerned by these detentions, as well as the extrajudicial killing of individuals suspected to be involved in drug activity in the Philippines," Trudeau said at a press briefing in Washington, a transcript of which was released by the State Department on Tuesday (Manila time).

"We strongly urge the Philippines to ensure its law enforcement efforts comply with its human rights obligations," she added.

The statement came two weeks after the state visit of US Secretary of State John Kerry, who met with the Philippines' newly elected president in Manila. Duterte revealed that he stopped Kerry from talking about human rights during their meeting at Malacañan.

"Iyong si Kerry nag-usap kami, human rights, [sabi ko] 'I have a job to do let us go to another topic'," Duterte said on July 31, speaking to members of the Presidential Security Group.

Trudeau, meanwhile, was reacting to a question by a journalist who observed the hundreds of people killed since Duterte came to office, including those suspected of links to the illegal drug trade.

The State official said the US emphasizes the importance of rule of law as a "democratic principle" and of due process in dealing with crime.

"We believe in due process. We believe in respect for universal human rights. We believe fundamentally that those aspects ensure and promote long-term security," she said.

The death squads believed to be behind some of the killings have been called a "murderous plague" by the Human Rights Watch. Archbishop Socrates Villegas, who leads Catholic bishops in the Philippines, also condemned the killings as "too much to swallow."

The United Nations' human rights body and anti-drugs office similarly urged the government not to condone the violent deaths.

Addressing concerns over rights violations, Duterte has said that while he does not want to see deaths, he has little care for human rights and his "mouth has no due process." On Sunday, he released a list of personalities in the police force, local government units and judiciary with alleged ties to illegal drug trade.