Cyber-security experts say Apple iOS users here could have downloaded apps infected with malicious software. They advised users to keep an eye out for suspicious activities or alerts on their iPhones or iPads.

They were commenting on the first major attack on Apple's App Store recently.

"While most of the affected apps were developed for the Chinese market, some are also available on other App Stores, so local users may be affected," said Mr David Siah, the country general manager for security software firm Trend Micro Singapore.

One such app may be messaging service app WeChat. "Those who are using the affected version of the app could be at risk. If users are unsure whether or not they have been exposed to the attack, the fastest way would be to check if their phone has been receiving any unsolicited or suspicious alerts via those apps," said Mr Siah.

These include alerts that send users to an unknown Web page or prompts that ask for passwords.

Palo Alto Networks' director of threat intelligence, Mr Ryan Olson, said the threat has been mitigated so far, as the infected apps are being removed by Apple.

But users should continue to be mindful about the apps they download, as the incident highlights a key security flaw in Apple's processes.

"Long term, we expect to see more attackers trying to get into the App Store by infecting legitimate applications in their development phase," said Mr Olson.

Mr David Emm, a senior security researcher from anti-virus software firm Kaspersky Lab, agrees.

"Apple's 'walled garden' approach does make it harder for cyber criminals to compromise apps, but if something does slip through the net, as in this case, there is no protection available because Apple does not provide third-party developers with the means to develop anti-malware protection for iOS."