REYKJAVIK -- Icelandic police said Wednesday they had shot and killed a polar bear discovered earlier this week on the island, which is hundreds of kilometres (miles) from the threatened species' natural habitat.

"It was shot last night (Tuesday)," a police spokesman in the northern town of Saudarkrokkur told AFP.

Polar bears are rare sightings on Iceland, since they have to swim hundreds of kilometres through icy waters to reach the island from their natural Arctic habitats, but the bear discovered Monday was the second spotted and killed on the island in the past two weeks.

Icelandic authorities had been harshly criticised for killing the first bear and had indicated they would try to capture the second animal, which was discovered by a 12-year-old girl as she was out walking her dog.

The chief veterinarian from the Copenhagen zoo had been flown in late Tuesday to help.

The police "tried to get close to (the bear) with our vet, but they did not get close enough to shoot it with the anaesthetiser," zoo spokesman Bengt Holst told AFP.

"Then the bear started running, so the police were frightened they would lose control. The bear could run very close to the populated area, so they decided to shoot it," he added.

Holst said he believed Icelandic authorities had made the right decision.

"It was a security problem," he said.

That two polar bears that have made their way to Iceland in recent weeks could lend credence to warnings from experts that climate change is creating a more perilous environment for the majestic Arctic animals.

A warming climate means the ice -- where the bears usually hunt their favourite prey, the seals -- is receding and literally melting under their paws, forcing them to swim ever greater distances.

Environmental and animal conservation groups have long warned the polar bear was in danger, and recent studies indicated melting Arctic sea ice could cut their population by two-thirds over the next 50 years.

The United States last month listed the polar bear as a "threatened species," meaning it is at risk of becoming "endangered" within the near future.

Animals are listed as endangered when they face imminent extinction.