Maksimus, who will turn ten in June, and his female companion Čaja, who turned ten last October, are two among 100 endangered Asiatic lions preserved as part of an European conservation programme.

There are only some 500 such lions still living in nature, according to the Ljubljana zoo.

To preserve the species, zoos from London, Helsinki and Zurich imported nine Asiatic lions from India in the early 1990s.

As a result, there are now around 100 Asiatic lions within the European Endangered Species Programme (EEP), a population management programme of the European Association of Zoos and Aquaria.

The two lions, which arrived in Slovenia in January from a Polish zoo, are also part of it.

They wil be kept at the new, 1,200-square-metre enclosure, the Ljubljana zoo's largest investment in recent years.

Yesterday's celebrations featured a number of accompanying events, including workshops where children could lean about big cats and also meet their keepers.

An exhibition tracing the zoo's development was also launched and the zoo was visited by Ljubljana Mayor Zoran Janković to inaugurate the lion's enclosure and cut a giant cake.