A zoo in Sweden has said it euthanised healthy lion cubs because it could no longer keep them.

Boras Djurpark, an animal park around 25 miles from Gothenberg, admitted it had put down nine healthy lion cubs since 2012.

Bo Kjellson, chief executive of the park, said healthy animals sometimes had to be euthanised if they were rejected by their pride, or cannot be rehomed elsewhere.

"I think they were killed after two years," Mr Kjellson told Swedish broadcaster SVT.

"At that time we had tried to sell or relocate them to other zoos for a long time but unfortunately there were no zoos that could receive them, and when the aggressions became too big in the group we had to remove some animals. And then it had to be them.

"It's no secret in any way and we do not try to hide that were working this way. So it's unfortunately a natural path for groups of lions."

Mr Kjellson said the zoo was unsure of what would happen to the other lions.

"That we will see in the future. Currently, the group works well, but some of them may become surplus animals, and then we will try to place them elsewhere.

"It could be so that we have to put them to death."

Only two of the 13 cubs, born to three separate litters, have survived the past five years.

Two lions died of natural causes and the remaining cubs were put down.

Helena Pederson, a researcher in animal studies at Gothenburg University, told SVT the euthanisation of animals in zoos raised the question of whether such institutions should be open.

"It is clear that there is a contrast to the public's perception of what a zoo is," she said.

"To kill animals as part of the organisation, I think that upsets quite a few.

"I think we need to contemplate on why it's important for us to have zoos and if it's worth the price the animals pay for it."