BEIJING -- China's Ministry of Public Security said on Saturday it has closed 31 websites and 1,100 social media accounts suspected of engaging in trolling activities or posting messages for extortion since the start of this year.

The police also busted 28 cases involving unlawful activities of paid online trolls, or ghostwriters hired to post online content, and arrested 67 suspects after a series of operations, said the ministry, adding that it found more than 80 enterprises and organizations were blackmailed.

In a statement, the MPS accused the suspects of engaging in extortion, fraud, running illegal businesses, causing trouble, libel, and violation of personal information.

Some suspects, by using social media platforms such as the microblogging service Sina Weibo and Wechat as well as setting up websites overseas, organized large-scale operations in paid post-writing, post-deletion and other activities, said the MPS.

The police found that some social-media account operators even fabricated trumped-up accusations against organizations and individuals, posted negative information online and demanded a "ransom-like" fee in exchange for post-deletion services.

Under some circumstances, these suspects would also hire other influential social media account owners and bloggers to hype up their clients, in violation of illegal advertising regulations, said the MPS.

The ministry said among the nabbed suspects, some have been given a jail term while some cases have been transferred to judicial organs