Sina Corp, which runs China's largest micro blog services, hit an unexpected second-quarter loss as it looks to capitalize on its mobile offerings and fend off competitors.

The Nasdaq-listed company posted a net loss of $11.5 million compared with a profit of $33.2 million a year earlier, according to a company statement on Tuesday.

The drop in profit masked a 20 percent jump in revenue, in which advertising income grew to $120.6 million, exceeding the company's expectations.