Some Norwegian fur farms let animals suffer with injuries such as bitten off legs or ears, an animal rights activists' group said after secretly videotaping dozens of farms.

The group, Network for Animal Freedom, said it had found examples of abuse at 45 fox and mink farms visited in recent weeks (www.forbypels.no). Norway has about 330 fur farms.

"We saw clear violations of animal welfare laws at all the farms we visited," said Per Arne Toellefsen of the network. He said that frustrated animals, cooped up in wire cages, often attacked and injured their own young.

Norwegian Agriculture Minister Lars Peder Brekk said a wide official review of fur farming in June had shown satisfactory conditions and did not lead to any prosecutions of farms.

"I'm concerned that we should still have fur farming in Norway but I'm very concerned that it should be done within the law," Mr Brekk told NRK public television.

The Network, which wants to ban fur farming, had also alleged abuse in a 2008 report. Mr Toellefsen said injured animals should be tended by a veterinary surgeon or put down quickly to avoid suffering. Common injuries were loss of a leg, ear or tail.

NRK visited a farm of 1,200 foxes and filmed one animal with a partly healed stump where a leg had apparently been chewed off.