Mobile Internet

Kaiser Kuo, a Beijing-based spokesman for the company, declined to comment on the options trading.

The HSI Volatility Index, which measures the cost of options on Hong Kong's Hang Seng Index, gained 4 percent to 15.69 on Friday. In the United States, the Chicago Board Options Exchange Volatility Index slipped 4.7 percent to 12.45 on Saturday, while Europe's VStoxx Index, which tracks Euro Stoxx 50 Index derivatives prices, added 0.3 percent to 16.31.

Chairman and Chief Executive Officer Robin Li said last month Baidu will buy mobile applications that supplement its search products, which had more than 100 million daily active users as of the first quarter.

Spending in the mobile Internet advertising industry in the Asia-Pacific region will increase 33 percent to $3.7 billion in 2013, according to data compiled by Bloomberg Industries. Total revenue from online advertising in the region will rise 16 percent to $29 billion this year, the data showed.

Biggest purchase

The Beijing-based company, whose cash and equivalents dropped to 8.73 billion yuan as of March 31 from 11.88 billion yuan at the end of last year, has made acquisitions valued at about $700 million in the past two years, according to data compiled by Bloomberg. Baidu is paying $370 million for the PPS Net TV's Internet video business, its biggest purchase.

"While this latest acquisition is not enough to truly move the needle in terms of earnings, we believe it is critical in that it gives investors something to consider other than deterioration of market share," David Riedel, president of Riedel Research Group Inc in New York, said by e-mail on May 14. "The market has been overly concerned about what we consider to be truly inconsequential competitive threats."

'Significant change'

A move by Alibaba Group Holding Ltd, China's biggest e-commerce company, to buy a stake in Sina Corp's Twitter-like Weibo service could weaken demand for Baidu's e-commerce search engine, Citigroup Inc analysts led by Muzhi Li wrote in a research note on April 30. Qihoo is hiring hundreds of engineers to develop its Internet browser and mobile-search functions as it competes with larger rivals such as Baidu and Tencent Holdings Ltd, Chairman Zhou Hongyi said in February.

Competitive threats to Baidu aren't as bad as investors fear, Ma Yuan, a Beijing-based analyst at Bocom International Securities Ltd, said by phone on May 15. The brokerage expects Baidu's mobile investments to start contributing positively in 2014, she said.