Last.fm says its free, on demand music streaming service has not only driven more traffic to the site, but been a commercial success for its retail partners.

The service, that was introduced in certain countries, the UK included, in January, lets users of the site stream songs from Last.fm's catalogue of five million tunes for free up to three times.

Rather than hurt music sales, Last.fm says overall CD and download sales through partner Amazon.com have increased 119%. And existing users are buying 66% more albums and individual tracks than they did before the free on-demand service debuted.

"In just over two months it's become clear that people will buy CDs and downloads if they get access to the kind of service we offer", said Last.fm co-founder Martin Stiksel.