iChinaStock News) Sina (NASDAQ: SINA) has shut down tens of millions of Weibo accounts that are used as zombie accounts to send spam messages or attack other users.

Charles Chao, CEO of Sina, said in a video interview with famous Chinese host Yang Lan today that Sina fights zombie accounts and spam on its popular microblog almost every day.

“Mostly, if zombie accounts do not hurt other users, we will not do anything. But if someone attacks other users–slander and defamation–we will take measures,” said Chao.

He disclosed that Sina has shut down “tens of millions” of accounts on Weibo. The Southern Metropolis Daily published a report on the growing phenomenon last month:

One wholesale distributor of fake accounts, who called himself “little hippo,” said he has over 10 million fake accounts on Sina Weibo and a team of over 10 people to maintain the accounts. He said he also has downstream distributors who advertise his service on microblogs and make transactions through online auction sites such as Taobao.

Sina runs China’s largest microblogging service, which has attracted more than 250 million users since its first launch in 2009. The new service, dubbed the Twitter of China, has created billions of market values for Sina.

This year Sina has intensified its efforts to tighten content control on Weibo as the service gains more and more social momentum that attracts government involvement.

In the interview, Chao said Weibo has helped China to become a more transparent society, noting that not only the Chinese government, but organizations and governments across the world are adapting to the rise of social networking.

He added that Sina is planning to launch a credit system that will encourage users to be more responsible for their opinions and behaviors online.