An ancient Chinese city wall with a history of more than 14 centuries is being eaten away by a kind of mite in Xi'an, capital of northwestern Shaanxi Province, archaeologists have said.

Experts were surprised to find it had been the mites undermining the wall at the Hanguang Entrance Remains Museum during their one-year research for further protection.

"The discovery is the world's first of this kind. The mites had damaged the wall seriously," said Li Yuhu, archaeologist of Shaanxi Normal University.