Chinese authorities blocked the country's two main microblogs, Sina Weibo and Tencent QQ, after six people were detained on March 30 for "fabricating or disseminating online rumors."
The two microblog sites announced on the websites they were acting to stop the spread of "rumors" and that the block on posting comments on the sites would remain in effect until April 3.
On March 30, Chinese authorities shut down 16 websites that were carrying posts suggesting military vehicles had entered Beijing and that a coup was under way.
China's state news agency reported that 1,065 people have been arrested in an Internet crackdown since February.
Some 208,000 "harmful" online posts have been deleted and 3,117 websites have been officially warned.
Based on reporting by Interfax and AFP