WASHINGTON, Aug. 8 (Xinhua) — The U.S. government on Monday expressed concern about what it called "extrajudicial killings" of drug suspects in the Philippines, while urging Manila to abide by human rights obligations.

"We are concerned by these detentions, as well as the extrajudicial killings of individuals suspected to be involved in drug activity in the Philippines," Elizabeth Trudeau, spokeswoman for the U.S. State Department, told a daily briefing.

The United States believes in rule of law, due process and respect for universal human rights, Trudeau said, adding that her country will continue its conversations with Filipino authorities "to emphasize the importance of this fundamental democratic principle."

In the latest effort in his massive anti-drug campaign since taking office in June, Philippine President Rodrigo Duterte on Sunday ordered more than 150 named judges, military and police officers and lawmakers, who are allegedly linked to drug crimes, to turn themselves in.

Duterte has ordered the police to crack down on drug lords and their protectors that allegedly include police officers and even the so-called "narco politicians."

So far, at least 600 people are reported to have been killed in the campaign against illegal drugs.