Smoking causes one in 10 deaths worldwide, a new study shows, half of them in just four countries - China, India, the US and Russia.
Despite decades of tobacco control policies, population growth has seen an increased number of smokers, it warned.
Researchers said mortality could rise further as tobacco companies aggressively targeted new markets, especially in the developing world.
"Despite more than half a century of unequivocal evidence of the harmful effects of tobacco on health, today, one in every four men in the world is a daily smoker [one in 20 women]," said senior author Dr Emmanuela Gakidou. "Smoking remains the second largest risk factor for early death and disability, and so to further reduce its impact we must intensify tobacco control to further reduce smoking prevalence and attributable burden."
That was a reduction from one in three men and one in 12 women who lit up in 1990. However, population growth meant there was an increase in the overall number of smokers, up from 870 million in 1990. And the number of tobacco-related deaths - more than 6.4 million in 2015 - increased by 4.7% over the same period.