China's Alibaba bans customers from using Tencent's WeChat

China's Alibaba Group, whose expected IPO could value the e-commerce company as high as $100 billion, has banned its customers from using Tencent Holdings' popular WeChat mobile messaging app to do business on Alibaba sites like Tmall and Taobao.

Some merchants have been using WeChat to directly communicate with customers and encourage them to do business outside of Alibaba's transaction systems, Alibaba Group said in a statement.

"We have therefore decided to temporarily suspend the subscription of WeChat-related applications in the seller-side service app market and encourage our sellers to conduct their marketing activities in a safe and legitimate manner," the company said.

In some cases sellers had also harassed other users. Alibaba said there is no timeline for when the ban might end, but it would "monitor the situation closely."

Tencent officials declined to comment.

WeChat, which has more than 300 million users in China and 70 million overseas, has usurped Sina Corp's Weibo microblogging service to become China's most popular social messaging app.