(Yicai Global) Sept. 1 -- Tencent Holdings Ltd. [HKG:0700], Sohu.Com Inc.[NASDAQ:SOHU] and Youku Inc. [NYSE:YOKU] have united to sue an online ad blocker, saying its developer is violating unfair competition laws.

Hangzhou Railway Transport Court heard the case in which the three internet firms are attempting to sue Hangzhou Shuowen Software Co. The defendant is the developer of LeWang, an online ad blocker, People's Court Daily reported on Aug. 31. The report did not disclose the outcome of the case.

All three plaintiffs have mainstream video sites in China which generate most of their revenue through advertising fees in its videos and membership fees paid by users to watch programs ad-free.

The trio found earlier this year that users can skip video ads completely by installing LeWang, and believe the ad blocker has destroyed their revenue model. They demand its developers compensate for losses of CNY1 million (USD152,000) each.

However, Shouwen Software said that LeWang targets malicious ads, and in the interests of its users, saves time, making it a public benefit.