Chinese buyer shows iPhone 6 and 6 Plus smartphones at a branch of China Unicom in Shanghai, October 17, 2014. [Photo/IC]

The China Consumers Association (CCA) has asked Apple to address a sudden shutdown problem associated with its iPhone 6 and iPhone 6s models in China.

According to a statement issued by the consumer protection organization on Tuesday, it has received a considerable number of complaints from users of both devices reporting that the smart phones have been shutting off automatically with 50 to 60 percent battery left. The bug persists after a system upgrade. It is also reported to have occurred in both cold environments and at room temperature. Some users complained that their iPhones, after shutting down involuntarily, failed to turn back on without connecting to a power supply.

"Given that iPhone 6 and iPhone 6s have considerable number of users and the problems have been reported by many, China Consumer Association has issued a query to Apple on the abnormal shutdown problem," the statement reads.

"CCA will follow the issue closely and protect the legal interests of consumers."

According to the organization, the questions raised to Apple include what caused the automatic shutdown, whether there is problem with the batteries, how the company will deal with the complaints and what measures the company will take.

So far, Apple hasn't publicly commented on the matter. CCA says it expects Apple to respond within ten days.