A customer tries on Apple's iPad mini, at an authorized store in Wuhan, capital of central China's Hubei Province, Dec. 7, 2012. Apple's iPad mini and the fourth-generation iPad went on the Chinese mainland market on Friday. [Photo/Xinhua]

China's commerce market watchdogs have called for tightened supervision of Apple Inc's disputed warranty policy in response to customers' complaints that the iPhone-maker adopted differential policies for repair and return services in China.

The State Administration for Industry and Commerce said it has issued a notice asking local industry and commerce authorities to enhance legal supervision over Apple's imparity clauses in its warranty policies.

The China Consumer's Association (CCA) has asked Apple Inc. to "sincerely apologize to Chinese consumers" and "thoroughly correct its problems."

In a statement on the CCA's website, Apple was told to equalize the warranty periods in China with other countries. Apple should inform consumers if refurbished parts are used when repairing broken devices, and repair costs should be counted accordingly, the statement said.

Apple products have gained huge popularity in China over recent years with China being the second largest market after the U.S. However, there are growing concerns that Apple has discriminatory after-sales service in China compared to the rest of the world.

In a special program to mark the International Day for Protecting Consumers' Rights on March 15, China Central Television (CCTV) accused Apple of offering shorter warranty periods in China compared with other countries and using refurbished parts for repair and averting after-sale obligations.

Consumers who asked for replacement of iPhones due to quality defects during the warranty period always found that their renewed iPhones still kept the old back cover, the program said.

In addition, the guarantee period was not extended to another year as stipulated in China's after-sale regulation but remained the same as with the former unit. Under Chinese law, replaced mobile phones should be covered by another one-year guarantee period after the replacement.

The CCA has unveiled a report detailing that complaints about after-sale service account for 25.6 percent of the total 2,170 complaints it has received about Apple products, 7 percentage points higher than the averaged data for the home appliance sector.