Nigeria's government says it has begun legal action against three leading international cigarette companies.
Smoking at a young age is a problem across Africa
It is demanding more than $40bn in compensation over their alleged role in promoting underage smoking.
The companies concerned are British American Tobacco (BAT), Philip Morris and International Tobacco Ltd.
A BAT spokesperson in London said children are not and never will be their audience and it believes the action is flawed and lacks merit.
BAT's Catherine Armstrong said it would vigorously defend the claim.
The government is also seeking an injunction compelling the companies to stop the marketing, distribution and sale of cigarettes to minors.
It says that products sold by the companies are addictive and hazardous to public health.
Cigarette smoking is widespread in Nigeria and BAT recently set up a factory in the West African country.
Correspondents say that over the past 20 years, tobacco companies have aggressively marketed their products in Africa and other developing regions to compensate for the loss of sales in developed countries that have imposed smoking restrictions.
The BBC's Fidelis Mbah in Lagos says the Nigerian government has in the past few years stepped up its campaign against smoking with the health warning "smokers are liable to die young" on cigarette packets and after radio and TV adverts.
Cigarette adverts have also been restricted, only allowed on radio and TV after 10pm, and billboards have been scrapped.
But our correspondent says tobacco sellers are still on the streets displaying their products for all to see.
Most children smoke in hiding after buying their cigarettes as there is no enforcement of a ban on the sale of tobacco products to underage children, he says.
One Lagos seller said he did sometimes sell cigarettes to children.
"But only to those who say they are sent by their uncles or fathers to buy," he told the BBC.
The World Health Organization estimates that 18% of young Nigerians smoke.