China's largest social app WeChat, with at least 900 million users, is using its vast social media network to lure high-end fashion brands including Longchamp and Burberry, according to the Wall Street Journal.

France's Longchamp and UK's Burberry Group PLC has started selling their products including handbags and clothes to WeChat users. Longchamp launched two in-app stores - one allows clients to customize their own products and the other to share customers' experience when visiting physical stores.

"We've seen the importance of WeChat," Jean Cassegrain, Longchamp's CEO, said, adding that the Tencent-owned app appears to be more effective compared with other e-commerce platforms. She also said that WeChat has indeed helped increased the brand's sales after Longchamp conducted a social media marketing experiment in China.

Meanwhile, Pablo Mauron, managing director for Digital Luxury Group in China, expressed doubt that "someone that doesn't have a relationship with a brand will buy a $20,000 watch on WeChat," adding that "People want to touch the product."

But Chinese tech publication Interface argued that brands opening WeChat stores are creating a unique loop - from initial contact with the brand to the purchase, and to a personalized customer service channel - something that is rarely seen outside of China.

Other big brands such as Louis Vuitton, Givenchy, and Dior are also testing the WeChat's waters through flash sales, Mashable reported.

Earlier this year, Tencent also customize its app to make it easier for brands to launch multimedia advertising campaigns and set up shops. Such move attracted more interest from luxury brands.

Tencent's latest push could be seen as a challenge to another Chinese e-commerce player, Alibaba. Online transactions of Alibaba-owned e-commerce sites are expected to reach $870 billion this year. China-based Alibaba, Tencent, and Baidu have all expanded beyond their respective core businesses - from payments to social media.