Image copyright Reuters Image caption KFC has over 4,000 restaurants in China

The fast food chain KFC is to sue three Chinese firms it accuses of using social media to spread false rumours about its food, including that it used eight-legged chickens.

KFC is seeking compensation of 1.5m yuan ($242,000, £159,000) and an apology.

One of the posts said chickens used by the company were genetically modified to have six wings and eight legs.

A case has now been filed before a court in Shanghai.

KFC says the rumours appeared in posts on the WeChat app.

Image copyright AFP Image caption Owner Yum Brands warned of a profit drop after a meat scandal hit its Chinese outlets

In a statement, the fast food giant said (in Chinese) that the rumours had spread through at least 4,000 subsequent posts.

"This not only seriously misled consumers, but also hurt our brand," said Qu Cuirong, KFC China's president.

The company named the original posters as Shanxi Weilukuang Technology Company Ltd, Taiyuan Zero Point Technology Company and Yingchenanzhi Success and Culture Communication Ltd.

Those firms have not commented on the court complaint.

By the end of 2014, KFC had 4,828 branches in China, and has been opening hundreds of new outlets every year.

The company's owner, Yum Brands, warned of a drop in profits for 2014 after one of the suppliers to its Chinese stores was accused of selling old meat.

KFC, along with fast food giant McDonald's, stopped using meat from the supplier after its operations were suspended last July.