Lawyers acting on behalf of Charles Gardella and other buyers filed a class-action lawsuit against 20 paper firms including UPM and International Paper, Norske Skog, M-real and Stora Enso pertaining to allegations of price fixing in the magazine papers market.

Stora Enso chief executive Jukka Hrml said it is "treating the issues seriously".

The action follows raids on major paper producers by European competition authorities and the US Department of Justice.

The lawsuit, filed at the US District Court in Bridgeport, Connecticut, said the firms had forced buyers to purchase paper at "inflated and supracompetitive prices" since January 1990.