Philippine President Rodrigo Duterte listens to speeches during the ASEAN Plus China Summit in Singapore last month. File picture: Bullit Marquez/AP

Manila, Philippines — Philippine President Rodrigo Duterte, whose controversial war on drugs has cost thousands of lives, says he uses marijuana to keep awake at long regional meetings, but later disavowed his assertion as a joke.

Duterte made the comment Monday at an awards ceremony where he talked about attending a recent summit meeting in Singapore of the Association of Southeast Asian Nations and how the daylong schedules of such gatherings are gruelling.

The 73-year-old Duterte said he used marijuana to keep himself awake at the ASEAN meeting. However, he later told reporters he was joking. Duterte is known for making blunt, off-the-cuff remarks.

Philippine police say more than 4,800 suspects have been killed in the drug crackdown that began in July 2016 and which rights groups have denounced as extrajudicial executions.