Environmental groups on Thursday blasted Finnish paper maker Stora Enso for logging old growth forests in northern Finland, insisting the unique trees should be protected.

Environmental groups Greenpeace, Suomen Luonnonsuojeluliitto and Luonto-Liitto said they had found that some trees more than 300 years old had been logged in Finnish Lapland in the north of the country and shipped to Stora Enso's pulp mill in Oulu.

The logged forests, also known as old growth forests or ancient woodlands, are owned by the Finnish state.

"It is unbelievable that at a time when forestry companies have slashed their production sharply, untouchable forests are logged," Risto Mustonen from Luonto-Liitto said in a statement.

Old growth forests are often home to rare, threatened and endangered species of plants and animals, making them ecologically significant.

Stora Enso said it had bought the wood from the state and admitted it was possible that some very old trees were included.

"We don't need ancient trees and our production cannot be based on that," Stora Enso's environmental manager Pekka Kallio-Mannila said.

Environmentalists have since 2006 urged Metsaehallitus, a state enterprise managing state-owned land and water areas, to conserve larger forests in the north. So far the parties have failed to reach an agreement.

Meanwhile, Metsaehallitus said the state had reviewed carefully its forests and noted that there were large conservation areas in Finnish Lapland as well.

"The forests in question are commercial forests. By no means are they old or indispensable forests," Metsaehallitus regional director Kirsi-Maria Korhonen said.

"The average age of those trees is not 300 years but between 80 and 200 years."

Stora Enso's Kallio-Mannila said deciding which forests to conserve was not easy and called for more dialogue with environmental groups and forest owners.

The forestry industry is important to the Finnish economy, accounting to nearly one-fifth of the country's exports.

The global financial crisis has further dented demand and profitability of Finnish paper makers, which have announced massive job and capacity cuts.