China's Sina Corp will launch a virtual currency for its highly popular microblogging service, Weibo, in the third quarter this year, the firm's first real push to monetise the platform, a source close to the matter said on Wednesday.

Sina, which launched Weibo about two years ago, has more than 140 million users. In a document released online recently, Sina detailed the use of its virtual currency, Weibi, for developers.

"Weibi is in the development stage now, but it will be launched very soon in the third quarter to a small portion of users before a full rollout later in the year," said a source close to the matter who declined to be named because the matter is not public. Weibi will have the value of one yuan and could be used to pay for virtual items and services.

The launch of the currency will be Sina's first major push to monetise the platform that has seen even Western celebrities, such as Tom Cruise, Radiohead, Bill Gates and Emma Watson, join.