Zhongsou.com, an online search engine provider in China, has filed a lawsuit against Yahoo (YHOO) at Beijing's Haidian District People's Court.

Zhongsou.com says in the petition that Yahoo deliberately eliminated features from Zhongsou's "Network Pig" software when upgrading its own search functions. This removal of features caused many users to complain to Zhongsou.

Zhongsou.com requests that Yahoo stop the infringement immediately, make a public apology and resume the function of Network Pig.

Yahoo China claims that it has not received any legal letters from either Zhongsou.com or the court.

Yahoo's operations in China are run by Alibaba.com.