Apple will launch an online payment service in China, media said, as the tech giant seeks to expand in its largest market outside of the US despite fierce competition from local rivals.

An Apple Company offering online payment has launched in the Shanghai Free Trade Zone (FTZ), an area set up as a testbed for financial reforms, China News Service reported late Thursday.

Apple didn't give a date for the launch, but the company told AFP that CEO Tim Cook hopes to set-up Apple Pay in China "as quickly as possible".

Cook previously said that he expects China one day to surpass the United States to become Apple’s largest market.

But China's e-commerce giant Alibaba dominates the country's online payment sector, with the Paypal-like Alipay taking around 80 percent of the market.

Internet firm Tencent is also catching up with a similar service provided via its popular messaging application WeChat.