E-cigarettes are fueling an "alarming" new wave of nicotine addiction, with millions of children now hooked on vaping, the World Health Organization warned Monday.

In countries that have the data, children are on average nine times more likely than adults to vape, the WHO said.

The U.N. health agency said the industry was promoting vapes as supposedly less harmful products than cigarettes — but in fact was aggressively targeting young people and getting children addicted.