SHANGHAI - The market size of China's online advertising reached 14.03 billion yuan ($2.22 billion) in the first quarter of 2012, according to survey results released on Wednesday.

The figure represents 56.2 percent year-on-year increase, and 5.6 percent decrease compared to the last quarter of 2011, according to the results of a seasonal survey of the online advertising market conducted by Enfodesk, a think tank that researches new media economics in China.

Baidu, Alibaba and Google China, the country's leading Internet companies, took the greatest advertising market share in the first quarter, the survey results said.

Sohu, Sina, Tencent and Netease, the country's largest Internet portals, took a market share of about 12 percent during the period, the results said.

The online advertising market in 2012 will largely be driven by major sports events, including the London Summer Olympics and the European Championship, according to Dong Xu, an analyst with Analysys International.