JD.com, China's largest online retailer, which reportedly sold refurbished iPhones, promised "a thorough investigation" of the case on Sunday.
A news report by China's state broadcaster CCTV said JD.com sold defective iPhones with fake components that may lead to complete shutdown of the phone.
In response to the report that went viral on social media, the eBay-styled company JD.com said in a brief statement that the supply channel of its iPhones is trustworthy and it will work with market watchdogs to thoroughly investigate the issue.
Apple overtook homegrown brand Xiaomi to become China's largest smartphone vendor in the first quarter of 2015.
In addition to authorized stores, Chinese customers can buy iPhones at all of the country's major online marketplaces.