Tmall, China's largest business-to-customer platform, sold half a million units of cell phones within 10 hours of launching its mid-year promotional campaign on Wednesday.

The online shopping promotional event was first created by Tmall's competito r JD .com Inc in 2010 as an annual showcase to celebrate its birthday. In order to compete with JD, many of China's major online retailer s have followed suit, which has made 618 a popular online shopping festival in China.

Tmall, which is famous for selling clothes, has been making effort to build up its reputation as a comprehensive online shopping platform. Through teaming up with cell phone makers in China, Tmall aims to establish itself as strong online platform in consumer electronics, an area which JD.com, China's second-largest B2C platform, enjoys an edge.

Among all the cells phones on sale at Tmall, Xiaomi , Huawei , inFocus and Coolpad, are the top sellers.

According to Tmall, about 40 percent of its overall online transactions on June 18 were made via mobile devices, signaling an increasing popular trend of mobile shopping in China.