Prosecutors in Beijing have brought charges against four men for operating bulk texting services without authorization, the Beijing News reported Wednesday.

Xicheng District prosecutors say the four suspects sent more than 10 million spam messages from Nov. 2008 to early 2010.

The spam messages contained promotion ads for real estate projects, private tutoring and information for fake invoice trade and credit cards service, the newspaper quoted prosecutors as saying.

The operators of the bulk texting services charged about 300 yuan (45.3 U.S. dollars) for sending 10,000 messages.

The four suspects -- Zhou, Shao, Xu and Xiang -- said they did not know bulk texting required a license.

China has no specific law on the sending of junk messages. However, the country's telecom regulation stipulates that all telecom value-added service providers should obtain a license before starting operations.

Bulk texting that contain ads is considered a telecom value-added service, according to Ren Lixin, a prosecutor in charge of the case.

According to Chinese law, if convicted the four could face up to five years in prison or more depending on the severity of the case.