Ruins of two moated cities dating back some 4,000 years have been found in a relics site in central China's Henan Province, local authorities said.

Archaeologists discovered two juxtaposed square-shaped cities, each surrounded by a moat, at the Yusi site in the city of Mengzhou. The one located on the east covers an area of about 60,000 square meters while the one on the west measures some 20,000 square meters, according to Zhang Xiaohu with the Institute of Cultural Heritage and Archaeology of Henan.

"It is worth noting that the depth of the moats exceeds 12 meters, which is too deep for normal defensive functions, indicating the importance of the two cities at that time," said Liu Haiwang, director of the institute.

An excavation drive was launched last April on the Yusi site, which covers an area of 1.5 million square meters and boasts cultural relics of various ancient dynasties. With the discovery of the two cities, Erlitou cultural relics have been found for the first time in northern and western Henan Province, experts noted.

Erlitou culture could be traced back 3,500 to 3,800 years in ancient China's late Xia (around 2070 BC-1600 BC) or early Shang (around 1600 BC-1046 BC) dynasties. It was named after the Erlitou relics site in the city of Yanshi, Henan Province. The culture spread widely throughout Henan and Shanxi provinces and later arrived in Shaanxi and Hubei provinces.