This has been a seventh such transport of animals in which military pilots train long-distance flights and landing on an unpaved ground.

Jaromir Sebesta, commander of the Czech air force, said the military CASA aircraft is not destined for long flights, but it offers sufficient comfort to the animals.

One of the four mares travelling to Mongolia is Saranqua, which was born in the Prague Zoological Garden as the 222nd young of the Przewalski's horse.

Two other mares come from German zoos and the fourth from Denmark.

Twenty-two mares and one stallion have been transported from Prague to Mongolia by a military plane since 2011. The project is financed from a fund to which Prague Zoo visitors contribute with two crowns per entrance ticket.

Twenty-five years will pass since the launch of the project of returning the Przewalski's horses into their natural habitat this year.

Prague Zoo director Miroslav Bobek says the salvation project is successful and that the horses reproduce in Mongolia.

The first transport to Mongolia was carried out in June 1992. Since 2011, the Prague Zoo has organised transports to western Mongolia independently. It has returned 27 animals to their original environment, including 23 from the Czech Republic and four within Mongolia.

This autumn or next spring, the Prague Zoo will take Przewalski's horses to China, but not in cooperation with the military.