It has been a long and winding road, but the Beatles are finally available on iTunes, filling a conspicuous gap in the digital music store's library.

The legendary pop group's 13 albums can now be downloaded through the world's number one digital music retailer, Apple has said.

A black-and-white photo of the Fab Four, with the text,"The Beatles. Now on iTunes" greeted visitors to the iTunes website.

The availability of the Beatles' hit albums like Sgt Pepper's Lonely Hearts Club Band, Revolver and Abbey Road is expected to give a boost to digital music sales this quarter and could possibly save their long-time record company EMI Group from defaulting on its debt in March, according to a person familiar with the situation.

The iTunes-Beatles agreement is exclusive into 2011, according to EMI, but the company declined to say when in 2011 it would expire.

The deal comes after years of fruitless negotiations between Apple founder Steve Jobs, Beatles management company Apple Corps and the Beatles label EMI.