BEIJING -- As a major government operation kicked off last week, the cyberspace watchdog on Monday named its ten top Internet extortion cases.

The case involving the 21st Century Media Ltd. topped the list of the China Cyberspace Administration (CCA). X Newspapers, magazines and the website affiliated to the group allegedly extorted more than 100 companies planning initial public offerings (IPO), threatening them with negative coverage unless they paid the group money. Last September, police arrested several of the media group's executives.

Four of the cases highlighted by the administration involved hackers or website operators accepting commissions to delete posts on forums or websites.

The most infamous of these was Yang Xiuyu, known by his screen name "Lierchaisi", who was convicted by a court in November for spreading false information and deleting posts for "clients". Yang was sentenced to four years in prison.

Two of the cases involved civil servants accepting bribes in exchange for helping certain parties delete information online: Gao Jianyun was a former senior official with the central Internet security and informatization leading group; and Wei Yining wa a police officer in charge of cyberspace security in Haikou, capital city of south China's Hainan Province.

Gao is under criminal investigation after being removed from the Party and his position. Wei was sentenced to ten years in prison.

Last week, the CCA started an anti-extortion operation, targeting Internet regulators and companies who take fees for deleting posts.

Websites that publish favorable stories in return for money have become commonplace, and some PR companies have made paid deletions their major business, according to Peng Bo, the administration's deputy head.

Some Internet regulators have abused their power and sought profit for exactly the same thing.

"We will show zero tolerance," Peng said.