BRUSSELS, Belgium - Eight out of ten Web sites selling mobile phone ring tones and graphics are tricking consumers with hidden fees or false advertising for free products, the EU said Thursday.

The EU's consumer affairs commissioner Meglena Kuneva said an Europe-wide investigation showed up shoddy sales practices such as hiding the true cost of downloads or not telling customers that they are signing up for a subscription.

"It's clear that consumers have been ripped off," she said.

She said she is telling national governments to go after crooked traders.

Ring tones - usually aimed at teenagers - make up almost a third of mobile content in Europe, racking up $1.1 billion in sales last year, the EU said.

With 495 million handsets, there is just over one mobile phone per person across the 27-nation bloc.

The European Commission checked some 500 Web sites, finding that 80 percent broke consumer advertising rules. It took action after receiving complaints from shoppers unhappy at being forced into subscriptions or extra charges.

"To be safe buying these services, check the fine print every time and make sure you are not signing up for more than you bargained for," Kuneva warned consumers.