Six years ago, more than a dozen men with AK-47s shot their way into Akinbode Oluwafemi’s home in Lagos, Nigeria. They killed his house guard and his brother-in-law, and briefly held a muzzle to the head of one of his year-old twins.

“I do not know why I was not killed that day,” said Mr. Oluwafemi, who as deputy director of Environmental Rights Action/Friends of the Earth Nigeria has been one of his country’s leading antismoking activists.

He was one of several tobacco control advocates at last week’s 17th World Conference on Tobacco or Health in Cape Town who in telephone conversations described violence or threats they faced as they fought the expansion of smoking in their countries.

No arrests were made in any case, and none of the victims could prove that the men assaulting or threatening them worked for the industry. But the pattern was consistent.