MANILA — President Rodrigo Duterte of the Philippines has ordered a sweeping ban on vaping in public, threatening to use the police and military to enforce what observers in the country have called a draconian order.

When Mr. Duterte, a former smoker, announced the ban in a speech on Tuesday, his statement caught many Filipinos by surprise but was largely ignored. But he reiterated the order on Wednesday in a long and at times rambling speech before the Department of National Defense, saying that vaping was “toxic” and could now be done only in private.

Mr. Duterte ordered the police to arrest anyone caught vaping in public in the Philippines, a largely Catholic nation in Southeast Asia that has some of the region’s toughest smoking laws.

Mr. Duterte said that many Filipinos, particularly young ones, used vaping devices without realizing the dangers they posed. This month, the Philippine Health Department reported the first case of vaping-related lung injury in the country. A 16-year-old girl was said to have been vaping for half a year before being hospitalized in October; she has since been released.