SOFIA (AFP) - – Bulgarian police have shut down four popular torrent websites in its largest ever action against Internet piracy, the international recording industry association IFPI said Monday.

The file sharing websites -- nanoset.net, rapidadd.com, 4storing.com and afasta.com -- were accused of illegally distributing books, films, games, music and software, IFPI said in a statement.

Run by an organised crime network, the four sites were probed for several months before their closure, it added.

According to Bulgarian police, which conducted the operation, users paid a total 5.0 million leva (2.5 million euros, 3.36 million dollars) in fees to get access to these services, the federation also said.

"Servers containing more than 120 terabytes of unlicensed content, or the equivalent of 200,000 CD-Rs," were seized by police during the raid, IFPI noted.

The Bulgarian Association of Music Producers, BAMP, praised the action.

"The sheer scale of this operation, the quantity of seized pirate content and the vast financial profit of the criminals involved shows clearly what an enormous problem piracy is in Bulgaria," Ina Kileva, executive director of BAMP, was cited as saying.

Bulgaria is the country with the lowest revenues from legal music and film sales in Europe, and a piracy rate estimated at 100 percent, IFPI added.