Rodrigo Duterte was sworn in on Thursday as president of the Philippines, promising to carry out an uncompromising crackdown on crime across the country.

Mr. Duterte said in his inaugural speech that the harm of corruption and drugs justified his tough approach, and he dismissed concerns that such a campaign would abuse the rule of law.

“I know the limits of the power and authority of the president,” he said. “I know what is legal and what is not. My adherence to due process and the rule of law is uncompromising.”