HELSINKI, Finland (AP) _ Unidentifed intruders released more than 7,000 minks from their cages in the middle of the night, the biggest raid on a mink farm in Finland, farmers and officials said Monday.

Police were alerted to the minks around 3 a.m. by a passer-by, Detective Chief Inspector Erkki Kerola said.

``We got a call from a person who said the area was swarming with minks,'' he told The Associated Press. ``Local inhabitants, the fire brigade and others are helping catch them.''

No one claimed responsibility for freeing the animals, which are used to make fur coats, Kerola said, but animal rights activists previously have released thousands of minks and foxes in 60 attacks on fur farms since 1995, claiming it's cruel to keep them in cages.

It was the first such raid on a farm in the region near Kokkola, 490 kilometers (30 miles) north of the capital, Helsinki.

``This was by far the biggest attack on a fur farm in this country,'' said Leif Finne, head of a fur farmer association. ``The farm had almost 8,000 animals and all the cages were opened.''

Some of the escaped minks were shot because they were injured.

``This is an ecological catastrophe,'' said Paivi Mononen-Mikkila, from Finnish Fur Sales. ``Minks will eat most anything smaller than themselves so birds and other wildlife are in danger.''

More than 5,000 people make a living from fur farming in Finland, the world's largest supplier of fox furs and Europe's third biggest producer of mink.

Last year, more than 2 million mink pelts were sold, mostly to overseas buyers.

In recent years, animal-rights groups have increased their activity in the Nordic region and thousands of mink have been set free in Sweden, Finland and Denmark.

On Sept. 5, some 8,000 animals were freed from a farm near Ringkoebing in western Denmark. Farmers were able to catch all but 1,000 of them.

Danish police suspected animal rights activists because the Danish acronym for the Animal Liberation Front was painted on a wall at the farm. No one was arrested.

Denmark is the world's biggest exporter of mink pelts.