BEIJING, Feb. 25 -- China on Sunday launched a three-month crackdown on Internet gambling, aiming to purify the cyber environment.

"The prevalence of online gaming has ruined the online environment and harmed young people's growth, which runs against the policy of building a harmonious society," said a circular jointly issued by the Ministry of Public Security, the Ministry of Culture, the Ministry of Information Industry and the State Press and Publication Administration.

Beijing, Shanghai, Guangdong and Zhejiang are key places to be supervised, it said, adding the government should clamp down on online games that involve gambling and online betting.

It said local government departments should strictly supervise online game service providers who are not allowed to exchange "virtual money" with real currencies or properties, or use it to launder money.

China's police busted a total of 347,000 gambling cases involving 1.099 million people last year and retrieved 3.56 billion yuan (445 million U.S. dollars) of money, according to official statistics.

Gambling was outlawed on the Chinese mainland in 1949 when New China was founded.