The Global Times reports that Alibaba Group will invest in Sina Weibo, buying between 15 and 20 percent in China’s most popular microblog. The report cites a former Alibaba staff member, Zhou Jinzeng, who said as much on his NetEase Weibo over the weekend. We'll let you know if we learn more. Update: We got in touch with Alibaba, who (not surprisingly) has no comment on the matter.

In Sina’s (NASDAQ:SINA) recent Q3 financial report, it disclosed that Weibo has surpassed 400 million registered users.