China United Network Communications Group Co Ltd, the parent company of China's second-biggest telecom operator, said the company had completed the building of the world's largest WCDMA 3G network by the end of 2011.

China Unicom said it owned a total of 237,000 WCDMA base stations in 2011, after it got the 3G network operation license from Chinese authorities in 2009, according to statement posted by China Unicom on Wednesday on the website of the State-owned Assets Supervision and Administration Commission of the State Council.

Between 2009 and 2011, China Unicom invested 129.3 billion yuan ($20.45 billion) in its 3G network. More than 85 percent of the investment was used to buy equipment from domestic companies.

Supported by China Unicom's investment, the country's telecom industry experienced a rapid development phase, which helped boost the nation's GDP growth and countered the negative impact of the 2008 financial crisis.

In May, the number of China Unicom's 3G users was 54.5 million, the company said.

Its operating revenue increased 24.8 percent year-on-year in the first quarter. The telecom service revenue grew 13.9 percent in the same period, higher than the industry average of 10.2 percent.

China Unicom also said the transactions amount of its online channel reached 23.1 billion yuan in 2011, with more than 100 million customers.