MANILA — He was a member of a hit squad that killed hundreds over the years, taking part in about 50 of the murders himself. One victim was fed to crocodiles, he recalled, and four others were hanged and thrown into the sea.

The self-described hit man, Edgar Matobato, said that Rodrigo Duterte, the new president of the Philippines, presided over the extrajudicial killings of about 1,000 criminal suspects and political opponents when he was mayor of Davao City for most of the past two decades — even ordering some of the killings himself.

“We were tasked to kill criminals every day,” Mr. Matobato said Thursday at a televised Senate hearing investigating extrajudicial killings under Mr. Duterte in Davao City.

Mr. Duterte’s promise during his presidential campaign to pursue his antidrug push nationally has alarmed human rights groups, which fear that extrajudicial killings are eroding the rule of law in the Philippines, an important American ally in Asia.