The platforms “are suspected of violating laws and did not fulfill duties to manage information published by their users,” the website continued.
Tencent shares in Hong Kong were in the red following the news. The stock was down more than 2 percent following earlier losses of around 4 percent.
Baidu and Sina trade in New York, and investors will be watching for any reaction at the U.S. market open.
CNBC’s Barry Huang contributed to this report.