The ban, which came into force on New Year's Day, outlaws sales of beverages with an alcohol content of 0.5 per cent or above to anyone under 18, according to a copy of the regulation on the Commerce Ministry's website on Friday.
Violators can be fined up to 2000 yuan ($250) for serious infractions. However, retailers have being given three months to implement the regulation fully, according to the official Xinhua News Agency. The ban is merely a regulation, not a law, and it wasn't clear how it would be enforced.
Many shops already display signs saying they don't sell alcohol to minors, but China has never had a formal ban on such sales. The only previous legal mention was a reference in the law on protection of minors that young people should be prevented from abusing alcohol.
Sociologists say rising under-age drinking has accompanied the growth of urban incomes and growing independence among children to indulge in the proliferation of restaurants, bars, karaoke parlours and other leisure outlets.
A quarter of middle-school pupils and up to 80% of high school pupils say they have drunk alcohol, according to figures cited by Sun Yunxiao, of the China Youth Research Centre, in a recent article in the official People's Daily newspaper.
"Alcohol abuse among minors has been pretty much ignored in schools and society as compared to drug use or even smoking cigarettes," Sun said.
"There has never been an effective mechanism like there is overseas for preventing the problem."
Along with banning under-age drinking, the Commerce Ministry's new Procedures for Regulating the Circulation of Alcohol also requires vendors to obtain licences for alcohol sales and to ensure alcohol purity and safety.