Philippine President Rodrigo Duterte has accused a dismissed police colonel, who publicly criticized him and his deadly anti-drug campaign, of criminal involvement and said he wants to know why the former officer "is still alive."

In a televised speech on Tuesday, Duterte condemned dismissed Senior Superintendent Eduardo Acierto, who told reporters that the president had been repeatedly photographed with two Chinese men involved in drug trafficking.

Duterte defended one of the two Chinese men, saying he had accompanied China's premier on a visit to the Philippines.

Acierto, a veteran anti-narcotics officer before his dismissal by an anti-graft agency, said he submitted a report about the two Chinese to police officials and Duterte's office but doesn't know if they were ever investigated.