BEIJING (AP) — Sina Corp., which operates a popular Chinese Internet portal, said Thursday its quarterly earnings tripled but cautioned that its fast-growing Weibo microblog service is unlikely to produce significant operating profit this year.

Shanghai-based Sina said profit for the three months ended June 30 was $33.2 million, or 49 cents per share, compared with $10 million in the same period a year ago. Revenue rose 10.5 percent over a year earlier to $131.6 million.

Revenues were hurt by a relatively soft Chinese advertising market due to slower economic growth, said CEO Charles Chao in a conference call. He said advertising revenue growth was expected to accelerate in the current quarter.

Sina offers entertainment, games and other content on the Internet and mobile platforms and operates Sina Weibo, the country's most popular microblog service.

Sina is starting to sell advertising on Weibo but is still investing to develop it and plans to start large-scale monetization next year, Chao said. He said Sina plans to launch a new version of Weibo later this year and add more services.

"We do not expect it will generate significant operating profits for the second half of this year as we continue to invest in our Weibo platform," Chao said.

The number of registered Weibo accounts reached 368 million by the end of June, up 13.6 percent from March, Chao said.

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Sina Corp.: www.sina.com