Internet giant Google has admitted that up to 260,000 smartphones have been hacked after handset users unwittingly downloaded virus-infected app, the AP reported Thursday.

The threat came to light last week when the technology giant was forced to withdraw at least 50 apps from its official Android Market, the report added.

According to the news agency, Google operated a 'killswitch' and remotely removed all of the affected apps from peoples' phones. The firm has now sent text messages warning those affected that the malicious applications could access their personal information and take control of their handset.

Studies have found that the dodgy applications were downloaded after they had been repackaged with a code that corrupted them.

Google Android is an open-source software stack for mobile devices that includes an operating system, middleware and key applications.

The deadly apps were simply copies of existing programs which had malware DroidDream found in them, and were swiftly taken off the site and recalled. But the damage was already done, affecting hundreds of thousands of users. .

Security expert Mikko Hypponen said the incident is embarrassing for Google because it shows the firm hasn't fully tested the safety of its apps.

'I do think Android phones are more vulnerable than any of the other major smartphones out there at the moment,' the Daily Mail quoted Hypponen as saying.