The first captive panda was released at the Wolong National Nature Reserve, 130 kilometers north of Chengdu. The rest were freed at Liziping Nature Reserve in Ya'an, southwest of Chengdu.

The release on Thursday has kick-started plans to enlarge the wild panda population in the Minshan Mountain range, as the Longxi-Hongkou National Nature Reserve has only 10 wild pandas, said Zhang Hemin, the center's deputy chief.

He said the center is planning a release soon in the Daxiangling Mountain range in Ya'an where the animal's population is also sparse.

According to China's fourth panda census, which was released in 2015, there were only 1,864 wild pandas in the world. The number was 1,596 at the end of 2002.