European bison are released at a reserve in Armenis, Romania, on Saturday. The animal was once nearly extinct. Adrian Piclisan / Agence France-Presse

Seventeen European bison were released into Romania's Carpathian mountain range on Saturday, one of the largest reintroductions of the endangered mammal in Europe.

The animals, which came from Sweden, Germany, Switzerland and Italy, were blessed by a local Orthodox priest in the southwestern village of Armenis, in the Tarcu mountains of the Southern Carpathians.

The event marked the return of Europe's largest herbivore in the Tarcu mountains 200 years after the last animals disappeared due to poaching.

"This is a very important day because usually we are used to losing species but today we are gaining a species in this area," Magor Csibi of the environmental group WWF told AFP.

The bison will first live in a re-wilding zone to learn necessary survival skills and also to form a solid social herd structure, the WWF and the Rewilding Europe group said.

In early September, these cousins of the American bison will be left completely in the wild, where they will coexist with deer, wolves and bears.

The European bison has recovered to a population of more than 5,000 after going extinct in the wild in the 1900s.

But only 3,400 of them live in free or semi-free herds.

Decimated by hunters and the loss of their habitat, the European bison bounced back thanks to a large-scale breeding program using the last survivors in captivity, whose offspring were reintroduced to the wild in areas of Central and Eastern Europe.

Poland now counts the largest population of bison in Europe, with more than 1,300 animals, according to the Warsaw-based European Bison Conservation Center.

In the long run, Rewilding Europe and the WWF hope to see the herd of the Tarcu Mountains grow to 500 animals.

"Increasing the number of bison is important, not only for the survival of the species, but also for biodiversity reasons," they said.