Beijing, Oct 9 (IANS): Police in China's capital city of Beijing have arrested some 30,000 suspects involved in cyber crimes in an online crackdown that began in 2011, a latest statistics report said Thursday.

According to Beijing's public security bureau, about 17 million illegal online messages were deleted in the three-year campaign, which also led to the detention of more than 50 suspects implicated in terrorism activities, Xinhua reported.

The clampdown targeted cyber crimes, hackers, online rumour-mongering as well as terrorism and violent content,the bureau said.

By June this year, police had deleted 3,300 terrorism-related messages and 728 audio and video files and e-books, the bureau added.

Police also stepped up penalties for operators who violated internet laws and regulations.

In 2011, around 1,000 operators were punished in accordance with the law.

The number soared to 11,000 two years later.

Official data showed that by the end of 2013, Beijing was home to more than 900,000 licensed websites, with about 70 percent of China's major web portals located in the capital city, and an online population exceeding 16 million.