iTunes users have downloaded over three billion songs from Apple's online music store.

"We'd like to thank all our customers who have contributed to this incredible milestone," said Eddy Cue, vice president of iTunes.

According to market research firm NPD Group's MusicWatch survey, iTunes recently surpassed both Amazon and the high street giant Target to become the third largest music retailer in the US, and is now the world's most popular online music, TV and movie store.

The online media store, which began selling just music for iPod users, now boasts a catalogue of over five million songs, 550 television shows and 500 movies.

The continued success of iTunes may surprise some naysayers after several issues, including lawsuits, security issues around its Quicktime component and reports that the new DRM-free iTunes Plus offering secretly recorded customer details and account information of the users who purchased the titles, hit the headlines.