BEIJING — Alibaba Group said yesterday it is buying all the remaining shares of mobile browser firm UCWeb in the biggest merger in Chinese Internet history, as the e-commerce giant steps up its spending spree ahead of its listing in the United States.

Alibaba’s latest deal, hot on the heels of a string of investments that already total US$4.8 billion (S$6 billion) in the past six months, will be larger than even Baidu’s US$1.9 billion acquisition of 91 Wireless last year, Alibaba said.

Alibaba already has a stake of about 66 per cent in UCWeb, an investment that emphasises the firm’s push to do more business on mobile in the world’s biggest smartphone market.

Its rival Tencent Holdings, China’s biggest listed Internet firm, dominates smartphone screens with its near-ubiquitous mobile messaging app WeChat, a situation which Alibaba executives have publicly railed against.

“This integration will create the biggest merger in the history of China’s Internet,” said Alibaba.

The cash and stock deal will see 3,000 workers join Alibaba as the business is fully integrated, the companies said in a joint statement, without specifying a price.

The two companies will form the UCWeb Mobile Business Group, to be responsible for Internet browsers, search services, location-based services, the mobile gaming platform, mobile application distribution and mobile literature services, UCWeb said.

UCWeb said the mobile search service had a market share of more than 20 per cent. It had more than 500 million mobile browser users and about 50 million customers at its app store last month. The Beijing-based company wants to reach one billion users in three years, with about half of them outside China, mostly by relying on its browser and search offerings, said its chief executive Yu Yongfu.

Alibaba is preparing for a US initial public offering that could value the firm as high as US$150 billion. Previous reports have speculated that Alibaba may launch its IPO on Aug 8, which is seen as an auspicious date.

But before that, the company will make its first appearance in the US with the debut of 11Main.com, an invite-only online marketplace that showcases small business retailers.

Bigger than Amazon and eBay combined, Alibaba has had no US e-commerce presence until now.

The site, which made its debut in a beta phase yesterday, will feature “hundreds of thousands” of products from 1,000 to 2,000 upscale speciality shops and boutiques around the country that were vetted by 11 Main. Agencies