The Copenhagen zoo that sparked international outrage by putting down a healthy giraffe and dissecting it in public has killed two lions and their two cubs to make way for a new male.

"Because of the pride of lions' natural structure and behaviour, the zoo has had to euthanize the two old lions and two young lions who were not old enough to fend for themselves," Copenhagen Zoo said in a statement.

The 10-month-old lions "would have been killed by the new male lion as soon as he got the chance," it said.

The four lions were put down yesterday after the zoo had failed to find a new home for them, a spokesman said, confirming the four were all from the same family.

There would be no public dissection of the animals since "not all our animals are dissected in front of an audience," he added.

Within a few days the new male will be introduced to the zoo's two female lions who, born in 2012, have reached breeding age.

"The zoo is recognised worldwide for our work with lions, and I am proud that one of the zoo's own brood now forms the centre of a new pride of lions," chief executive Steffen Straede said.

Last month, zoo boss Bengt Holst received death threats for the decision to kill its 18-month-old giraffe Marius, which was put down with a bolt gun before children were able to watch it being chopped up, dissected and fed to lions.

The move shocked thousands of animal lovers around the world who had signed an online petition to save him.

The zoo said on its website it had no choice but to prevent the animal attaining adulthood since under European Association of Zoos and Aquaria rules, inbreeding between giraffes is to be avoided.

Many Danes were surprised and even angered by international reactions to the event, with a leading expert on the ethics of the treatment of animals decrying the "Disneyfication" of zoo creatures.