Two more luxury brands have planted their flags in China’s online e-commerce space by setting up virtual shops on Alibaba Group’s Tmall.com.

Upscale American apparel label Calvin Klein and German luxury menswear brand Hugo Boss this week announced their debut on Tmall, China’s largest B2C shopping website. The retailers are following in the footsteps of Burberry, which became the first luxury label on the Tmall.com platform when it opened its store in April.

Luxury brands have been reluctant to open up online sales channels because of the importance they place on brand image and the personal experience of shopping. E-commerce has also been perceived by upscale brands as discount oriented and devoid of the sense of prestige that comes with shopping in a boutique.

That outlook may be changing. According to an April report from McKinsey, global online luxury sales amounted to $11.3 billion in 2013, which is just a fraction of total worldwide luxury goods sales. As more upscale retailers try e-commerce, online sales are expected to more than double to at least $22.5 billion by 2018. “Pure online transactions still represent only about 4 percent of the total luxury goods market, but they’re growing twice as fast as the sector as a whole,” McKinsey said in its report.

Hugo Boss rolled out its Boss Orange apparel line on Tmall.com store on Nov. 19. Boss Orange is a casual apparel line offering trendy leather jackets and graphic T-shirts targeting a younger demographic. To mark the launch, the company is offering Chinese shoppers coupons and discounts and giving away freebies to entice users to spend more.

Calvin Klein, which soft-launched its Tmall.com store back in September, officially launched it this week. The store sells Calvin Klein Jeans and Calvin Klein Underwear.

Luxury spending in China has declined this year, falling one percent, said an October Bain & Company report.