CHINA'S largest search engine operator Baidu said it is acquiring smartphone apps distributor 91 Wireless for US$1.9 billion, making it the country's largest Internet acquisition deal.

Baidu has signed a memorandum of understanding with NetDragon Websoft Inc to buy a 57.41 percent stake in 91 Wireless from the Hong Kong-listed company and has also agreed to take the remaining stake from other shareholders upon their approval, according to a stock exchange filing yesterday.

91 Wireless serves as a third party mobile application distribution site and it allows owners of smartphones with either Android or iOS operation system to easily access and manage the mobile applications on their mobile devices.

It's the largest third party application distribution platform by number of active users, according to an iResearch report.

Baidu has been pushing its mobile traffic in the past few years and stepping up collaboration with mobile software developers by offering them incentives in order to attract users and fight off rivals like Tencent and Sina.

"The deal will allow Baidu to have a better relationship with application developers on 91's distribution platforms and strengthen its position in the mobile Internet sector," said independent industry commentator Liu Xingliang.

Mobile app stores have become an important channel for Internet visitors.

The number of mobile Internet users in China had jumped 18.1 percent from a year ago to 420 million by the end of 2012, and it remained the most widely used method to access the Internet among around 600 million web users, according to the state-backed China Internet Network Information Center.

This year has seen a number of investment deals in the Internet sector as big companies step up efforts to extend their reach and power to the mobile Internet sector.

Alibaba, China's largest e-commerce company, said in May it is acquiring a 28 percent stake in online mapping company AutoNavi Holdings Ltd for US$294 million. The e-commerce giant also purchased 18 percent of Sina's popular microblogging service, Weibo, for US$586 million in April this year.