NHN Corp., South Korea's biggest Internet portal operator, aims to launch its social networking service in China this year, officials said Thursday. 

NHN Japan Corp., a subsidiary of NHN, hopes to introduce LINE to the world's fastest growing smartphone market, as the company targets 100 million users worldwide this year, the company officials said. 

In June 2011, The company released LINE, a free group messenger application for mobile phones, including iPhones and Google's Android-based phones. 

Since the launch, LINE has risen to become one of the most popular applications for mobile devices in many Asian countries. 

As of Thursday, its number of users topped 50 million, the officials said. 

The 50 million-milestone was reached in just 399 days, much faster than other social networking service applications. Drawing that many users took Twitter 1,096 days and Facebook 1,325 days. 

The application saw the fastest-growing number of users in Asia, including the Middle East, and most recently in Russia. 

The company attributed the rapid growth to the application's unique features, including a free call function and emoticons and stamps, which add a personal touch to the user experience.

LINE has at times ranked at the top of Apple Inc.'s online application stores in Hong Kong, Taiwan, Singapore, Malaysia and Japan, NHN officials said. (Yonhap News)