Marcus Barton: "If I hadn't had a rifle, I wouldn't be here now"

Marcus Barton, 32, who recently graduated as a dentist, was leading the Royal Geographical Society-approved expedition to the Arctic.

Marcus Barton: Forced to shoot

He has described how he was forced to kill two bears when they attacked his group.

The 17-strong party of students on the mountaineering and geological expedition on the Svalbard Islands came under attack on two consecutive days.

Mr Barton said the first animal approached the camp on Saturday looking for food.

Speaking on BBC radio he said: "We did everything we could and went to incredible lengths to deter him.

"We used pyrotechnics, live ammunition fired into the ground, flares, thunder flashes, even banging mess tins together - nothing seemed to deter him.

Horrendous experience

"In the end unfortunately the bear charged my colleague who fired a shot into his leg and then very quickly in the next five or six seconds we killed the bear."

Mr Barton said it was a horrendous experience and not one he would ever wish to repeat.

But only 36 hours later he was forced to do the same thing when a second bear entered the camp.

"The second one was worse because it approached in a very straight line to our camp," he said.

When the group tried to scare off the bear by making a noise this provoked the animal and it attacked them.

Bears usually eat seals

He said: "It charged the base of a mound just in front of us where it went out of sight, which was very unnerving.

"We had about 40 seconds of wondering where this polar bear was, knowing it was probably only 30 metres away.

"In the end it popped up over the centre of this mound we both made eye contact and it charged.

Douglas Richardson: Hungry bears can be dangerous

"I shot it when it was about six metres from me.

"It was a traumatic experience and the effect on the camp was devastating.

"I would never, never in my worst nightmares anticipated having to kill a bear let alone two bears."

London Zoo's Douglas Richardson: Bears are very intelligent

At this time of year, polar bears normally eat seals, but melting snow has meant they are hard to find.

London Zoo's Douglas Richardson said hungry polar bears could be very dangerous.

Members of the group have been interviewed by local police about the incident but Erik Nygaarb, a police inspector on the Svalbard Islands, said they seemed to have acted "within the law."

Polar bear hunting has been banned in the country since 1972 although Norwegian law allows killing in self-defence.