Shenma, the mobile search unit of Alibaba has filed a lawsuit against Sogou for traffic hijacking, local media has reported (in Chinese).

In the filing, the mobile search company accused Sougou of misleading and reeling in potential Shenma users through Sogou Input Method. Shenma is seeking RMB 100 million ($16 million) in compensation.

The lawsuit marks a collision between two of China’s most popular mobile search services. Shenma and Sogou took the second and third spot in China’s mobile search sector (in Chinese), representing 18.5% and 15.2% of the market respectively. Baidu still topped the list with 64.3%, according to data from third part research institute Big Data Search.

Actually, this is not the first time that Sogou was sued for unfair competition. In 2014, Baidu sued Sogou for similar issues, claiming Sogou’s integration of search functionality in its Chinese character input method editor was effectively hijacking Baidu’s search engine traffic. The court ruled in favor of Baidu and Sogou has paid an damage or RMB 500k.

On another hand, this case reveals the proxy war between China’s internet titans Alibaba and Tencent in yet another vertical. Shenma started in 2014 as a joint venture between Alibaba and mobile internet software service UCWeb, which Alibaba fully acquired later in the same year. Tencent is Sogou’s biggest stakeholder with 43.7% after initially investing $448 million for 40% in 2013. The Chinese search engine went public in the US last year.