Apple is taking steps to remove malicious iPhone and iPad programmes found in the Chinese iOS App Store.
Various cyber-security companies identified a malicious programme, known as XcodeGhost, which enables hackers to gather data from devices.
The programme was found in several apps used by owners of iPhones and iPads in China including Tencent’s WeChat messaging and calling app.
Apple spokeswoman Christine Monaghan said in an email, "We’ve removed the apps from the App Store that we know have been created with this counterfeit software.
"We are working with the developers to make sure they’re using the proper version of Xcode to rebuild their apps."
Tencent said that the security issue impacts an older version of the WeChat 6.2.5 app. The company said the latest versions were not affected.
US cyber security firm Palo Alto Networks said several users were affected by the infected apps.
The company said: "We believe XcodeGhost is a very harmful and dangerous malware that has bypassed Apple’s code review and made unprecedented attacks on the iOS ecosystem."
Earlier this month, cyber-thieves stole login names and passwords for over 225,000 Apple accounts in China.
