(CNN) Philippines President Rodrigo Duterte said that when he asked for six months to end the country's drug problem in 2016, he didn't appreciate the levels of pushback and corruption he would find in the government.

Duterte told the CNN affiliate his opponents' criticisms were "stupid remarks coming out of an empty head" and added that every country is tackling a drug problem.

"It is a neverending war ... (When I came to power) I expected everybody was working well," he said. "I did not know when I arrived, when I got to look into the records of drug cases, then I realized that I was fighting against my own government, because of the police, the customs, and everyone else were dipping their dirty fingers into it."

Duterte has waged a controversial all-out war on drugs in the Philippines since coming to power in June 2016, which police say has claimed the lives of more than 6,600 people. Independent monitors believe the number could be much higher than that. The United Nations Human Rights Council voted in July to open an investigation into the killings.

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