(Adds CEO's comments, comparisons and earnings details)
Aug 14 (Reuters) - Chinese internet firm Sina Corp posted better-than-expected growth in both revenue and earnings on Thursday, riding a strong performance from its Weibo Corp online messaging subsidiary and a 29 percent jump in advertising sales.
Shares in the company rose about 5.3 percent to $50.40, up from a close of $47.82 on the Nasdaq.
The results are a shot in the arm for recently struggling Sina, which booked a $33 million loss in the first quarter as larger or faster-expanding Chinese rivals like Alibaba, Tencent and Baidu vied for traffic and advertising.
Excluding Thursday's after-hours gain, Sina's stock had been down more than 40 percent since 2014's start.
"Weibo is executing well with strong financial performance, solid traffic growth and measurable progress toward building out a social commerce platform and offering native ads to large-brand customers," Sina CEO Charles Chao said in a statement.
Weibo, the company behind what's often described as China's Twitter, more than doubled its revenue in the second quarter, as usage and traffic grew.
Sina's revenue on a non-GAAP basis climbed to $184.4 million, up 21 percent from $152.8 million a year earlier and surpassing the $179.2 million that Wall Street had expected.
Net income attributable to the company, on a non-GAAP basis, slid 15 percent to $12.1 million or 17 cents a share. But that tidily beat forecasts for 9 cents, according to Thomson Reuters I/B/E/S.
It forecast net revenue on a non-GAAP basis of $193 million to $199 million, versus an average forecast for about $199.12 million.
(Reporting by San Francisco newsroom; Editing by David Gregorio and James Dalgleish)