Is Alibaba Group Holding Ltd. planning a takeover of Sina.com's Weibo microblogging service?

The e-commerce behemoth just acquired another three million American Depository Shares of Weibo Corporation from the company's management team for a total of US$135 million, increasing Alibaba's stake in the Twitter-like service to 31.5% from 30.1%, according to a Securities and Exchange Commission filing.

But unlike Twitter, Weibo is not blocked and filtered in China. Plus Weibo's features include many more Chinese-friendly features than the troll-ridden Twitter, which is based in the United States, and Weibo offers marketers good access to key opinion leaders. And Alibaba's move could be geared toward further stake purchases as Alibaba may eventually take over the whole company, as it did with online video site Youku Tudou.

Alibaba initially purchased 18% of Weibo for US$585.8 million in 2013, followed with another stake acquisition in 2015 to increase its interests to 30%.

Following the latest transaction, which took place on August 31, Alibaba now owns an equivalent of 67.9 million Class A shares, comprising 58.9 million Class A shares and 9 million ADSs.

This corresponds to 68.1% stake of Class A shares, or 31.5% of Weibo's total outstanding shares and 15.2% voting power.