The number of smartphone viruses saw an "explosive increase" over the past year, an anti-virus report said on Tuesday. More viruses targeting mobile devices are expected to be released this year.

More than 800,000 newly developed smartphone viruses were detected in 2013, "dozens of times" higher than the previous year, according to an annual report released by cyber security provider Beijing Rising Information Technology Co.

Apps embedded with malicious functions that are capable of stealing private information or deducting fees without advance notice were among the top threats, Rising said.

Devices running on Google's open-source Android operating system were the most popular targets for malicious apps because it has a number of versions and it's difficult for all the owners to update.

Android is the most-used OS globally for smartphone users, with about 75 percent of the market share, industry research shows.

Anti-virus experts at Rising warned that an even larger number of viruses and malicious apps are likely to enter the market this year.

Rising also found that 23 million personal computers were attacked and more than half of Chinese netizen accidentally downloaded virus software to their computers in 2013.