Sina Corp. has reportedly engaged Credit Suisse and Goldman Sachs to lead a $500M US IPO for its Sina Weibo microblogging service. In a related development, Alibaba Group Holding, the largest Chinese e-commerce company, is reportedly set to increase its 18% stake in Weibo (purchased last year from Sina for $586M) to 30% if an IPO takes place. Alibaba itself is also said to be considering an IPO in Hong Kong or the US. These are further signs of the intensifying competition among China's Internet giants to attract the rapidly growing number of Chinese using mobile devices to access the Internet. Weibo's main competitor is Tencent Holdings, owner of the popular We Chat instant messaging app.