A group of 23 bison has been released into the Carpathian Mountains of Romania, the biggest batch yet in an ambitious scheme to re-establish the species in the wild.

The European bison, a hulking beast which stands six feet tall and can weigh up to 2,000lb, disappeared from Romania two centuries ago.

Conservation groups are determined to re-establish a viable population in the Carpathians and hope to build the population up to at least 100.

The 23 bison, which came from zoos and nature reserves in Germany, Italy and Romania, were released at two sites by WWF Romania and Rewilding Europe, a conservation organisation that campaigns for the return of wilderness across large swathes of the continent.

The bison reintroduction scheme began in 2014, since when several small groups have been gradually released. This latest release was by far the largest.