Weibo, which operates like Twitter and allows users to post short messages and gather followers, has more than 250 million users, who often use it to vent about topics China's government deems sensitive such as corruption and the status of Taiwan.

In December, the Beijing city government issued rules giving microblog operators based in the city, which include Sina, three months to ensure users register their real identities.

Users must link their mobile phone numbers to their Weibo account and only those verified will be allowed to post messages. Sina has said the regulations would hurt the platform.

"We estimate that by the deadline, the majority of our users, about 60 percent of them would have successfully registered their identities," Liu Qi, a Sina spokesman, said.

China has repeatedly criticized microblogs for spreading what it calls unfounded rumors. The country blocks social networking sites such as Twitter and Facebook, citing the need to maintain social stability.

(Reporting by Melanie Lee; Editing by Kazunori Takada and Miral Fahmy)

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