Simpson Thacher & Bartlett and Skadden, Arps, Slate, Meagher & Flom have had the lead roles on Chinese e-commerce giant Alibaba Group Holding Ltd.’s buyout of mobile web browser developer UCWeb Inc.

Alibaba, which already owns 66 percent of UCWeb, is buying the remaining shares. Terms of the deal were not disclosed, but the Wall Street Journal reported that UCWeb chief executive officer Yu Yongfu told staff at an internal meeting that the deal valued the company at more than double the $1.9 billion Alibaba rival Baidu Inc. paid to acquire smartphone app store 91 Wireless Websoft Ltd.

Hong Kong partner Kathryn Sudol led a Simpson Thacher team representing Alibaba. Skadden Hong Kong partners Julie Gao and Will Cai and Beijing partner Daniel Dusek advised UCWeb.

Beijing-based UCWeb is the developer behind the UC Browser, one of China’s most popular mobile browsers, with over 500 million users worldwide. The deal will see Alibaba integrate the browser, search engine and app store into its own mobile operations, of which Yu will become head.

The deal is latest sign of the intensifying competition among China’s leading Internet companies: Aliababa, Baidu and Tencent Holdings Ltd. UCWeb is a direct competitor to Tencent’s QQ Browser. Earlier this year, Alibaba and UCWeb also jointly launched mobile search engine Senma to compete with Baidu, China’s leading search engine.