Authorities in Beijing have issued new rules requiring users of microblog sites to register personal details.
New users of Weibo - Chinese equivalents of Twitter - will now have to submit their real names. Existing users have to register in three months.
Those who refuse to do so will lose the ability to publish microblog entries.
The move comes with Chinese people increasingly using Weibo platforms to criticise government policies or vent anger over particular incidents.
Some Weibo entries are censored - such as ones that relate to the ongoing unrest in southern China's Wukan Village.
But Chinese authorities have accused netizens of spreading rumours on Weibo in the past and have long been discussing putting in place a "real name mechanism".
Liu Ruisheng, a media researcher at the official Chinese Academy of Social Sciences, argues that that improper Weibo usage is a widespread phenomena.
"Real name accreditation for Weibo sites is yet to be made universal; anonymous and irresponsible 'micro communication' is indeed fanning the spread of rumours," Mr Liu told the China Youth Daily.
The new regulations - which take effect immediately - were issued jointly by Beijing's information, communication and police authorities, and published on the city's official news portal.
Websites that are registered in the capital will have to follow the 16-point regulations and make their Weibo users register their personal data.
Two of the main Weibo services - Sina and Sohu - will have to follow the new order immediately as they are both registered in Beijing.
Sina Weibo on its own has more than 200m registered users both in China and overseas.
Tencent - another major operator - is registered in the southern city of Shenzhen, where "real name" regulations do not currently exist.
Before Friday's announcement, microblog sites such as Sina Weibo already requested that users supply personal details such as identity card or passport numbers for password-retrieving purposes. But those who preferred not to did not have to give this information.
Some users on Sina Weibo have expressed unhappiness at the new rule, posting messages such as "goodbye Weibo" and "time to move on" and calling on friends and followers to migrate to other social media sites such as Twitter and Google+ instead.
"Netizens cannot win - when the authorities are in a good mood, they treat you as a joke; when they're in a bad mood, they censor you," one user from Xian city wrote. "Netizens' right to free speech is not even a consideration for them."