Apple has sold one billion songs through its iTunes Music Store, a new benchmark figure for digital music sales.

The one billionth song was sold in the early hours of Thursday morning. It has taken Apple less than three years to achieve the landmark figure. iTunes Music Store opened for business in the US on April 28, 2003.

The front page of Apple's website now proclaims "To every iTunes Music Store customer, thanks a billion," and confirms the download figure.

To help achieve the figure, Apple launched a special competition this month: "As we marked our way to one billion, the music fans who downloaded every 100,000th song won a prize package featuring a black 4GB iPod nano and a $100 iTunes Music Card," the company explained.

The music lover who downloaded the billionth song won a new 20-inch iMac, ten 60GB iPods, and a $10,000 iTunes Music Card. A music-school scholarship will also be set up in their name, the company has said.

As the grand prize loomed, Apple saw iTunes song sales exceed 3 million tracks a day, dwarfing other digital music service operators.

The record figure is all the more remarkable when you consider that Apple began its countdown to half a billion songs in July 2005, which means the company has doubled sales volumes in under one year.

At that time, Apple CEO Steve Jobs said: "Just over two years ago, we sold our first song. Yesterday, we sold our half billionth song. Wow! As we cross this major milestone, we couldn't be more excited about the future of digital music, iTunes and the iPod."

The names of the prize winners haven't yet been revealed. An Apple statement on its new sales record is expected.