YINCHUAN- The West Xia Tombs, an ancient imperial tomb complex in Northwest China's Ningxia Hui autonomous region, has started a project to bid for world heritage status, local authorities said.

The site is expected to be included in UNESCO's World Heritage List in 2015, according to the State Administration of Cultural Heritage on Wednesday.

Located at the foot of the Helan Mountains, 30 kilometers west of the regional capital of Yinchuan, the site includes nine imperial mausoleums and more than 250 tombs of imperial relatives and officials of the West Xia Kingdom (1038-1227).

Covering an area of more than 50 square kilometers, the burial complex is considered one of the largest imperial tombs discovered in China, and it is also referred to as the "oriental pyramid" by some archaeologists.

The site was listed as a key cultural relics protection unit by the State Council in 1988 and was inscribed in the state natural and cultural heritage list in 2006.