A polar bear that swam more than 200 miles in near-freezing waters to reach Iceland was shot on arrival in case it posed a threat to humans.

The bear, thought to be the first to reach the country in at least 15 years, was killed after local police claimed it was a danger to humans, triggering an outcry from animal lovers. Police claimed it was not possible to sedate the bear.

The operation to kill the animal was captured on film.

The adult male, weighing 250kg, was presumed to have swum some 200 miles from Greenland, or from a distant chunk of Arctic ice, to Skagafjordur in northern Iceland.

"There was fog up in the hills and we took the decision to kill the bear before it could disappear into the fog," said the police spokesman Petur Bjornsson.

Iceland's environment minister, Thorunn Sveinbjarnardottir, gave the green light for police to shoot the bear because the correct tranquiliser would have taken 24 hours to be flown in, the Icelandic news channel Visir.is reported.

Sveinbjarnardottir's account was disputed by the chief vet in the town of Blönduó, Egill Steingrímsson, who said he had the drugs necessary to immobilise the bear in the boot of his car. "If the narcotics gun would have been sent by plane, it would have arrived within an hour," he said. "They could keep tabs on the bear for that long."

Steingrímsson also criticised police for not closing a mountain road where people congregated after hearing news of the bear. "There were around 50 to 60 people there watching. The police did not have many options when the bear ran down the hill, approaching the crowd," Steingrimsson said. "I'm very unsatisfied that the police did not try to catch it alive and did not close the road."

The oldest record of polar bears being sighted in Iceland is from 890, 16 years after the first settlers arrived. The last visit was in 1993, when sailors saw a bear swimming off the coast of Strandir. It was also killed.

Polar bears were frequently tamed during the middle ages, but since then no bear has been captured alive in Iceland. Receding North Pole ice is diminishing their hunting and mating grounds and jeopardising their survival.

A spokesman for PolarWorld, a German group dedicated to the preservation of the polar regions and the creatures which inhabit it, called the bear's death "an avoidable tragedy ... another great day for mankind".