A Norwegian court sentenced five men to prison terms ranging from six to twenty months in a landmark case on illegal wolf hunting.

The harshest sentence was handed down to Dennis Roger Nordahl who was found guilty of killing a wolf on March 14, 2014. He claimed that he had mistaken the animal for a fox.

All five men were also found guilty of hunting and shooting at three other wolves without harming them the next day.

Wolves have conservation status in Europe and can only be hunted in special circumstances.

"This is an historic judgement," Nina Jensen, head of the conservation group WWF in Norway told public broadcaster NRK.

"Never before has someone been convicted for illegal hunting," she said, adding that she hoped the ruling would act as a deterrent to other illegal hunters.

The case against the men was backed up with police surveillance of telephone calls.

Wolves are protected in Europe under the 1979 Bern Convention as well as the European Union's Habitats Directive. Norway had between 34 and 36 wolves at the last count and a further 39 living between Norway and neighbouring Sweden and Finland.

Since 2010 Norway has included wolves on a list of species in critical danger of extinction and hunting is only allowed in exceptional cases where the predators threaten livestock.

Nonetheless, researchers believe most wolves in Sweden are killed in illegal hunts.

The Norwegian Association of Hunters and Anglers said it "totally distanced" itself from the convicted hunters who have appealed the ruling.