Apple China will offer free battery replacement for certain faulty iPhone 6s that shut down unexpectedly.

Consumers across China have filed complaints on China's microblog service Weibo, claiming their mobile phones unexpectedly switch off despite displaying battery levels over 50%.

China Consumer Association earlier last week sent a letter to Apple, requesting that it clarify the reason.

Stressing the issue is not safety-related, Apple China said in a statement Monday morning that the unexpected power-off only affects handsets with certain serial numbers. It agreed to replace the batteries of faulty iPhone 6s manufactured between September and October 2015 free of charge. Other models with the same problem are not included in the current replacement plan.

Consumers can check whether they qualify for free battery replacement at any Apple store or authorized reseller, the company added.