YINCHUAN, May 18 (Xinhua) -- Archaeologists in Ningxia Hui Autonomous Region, northwest China, have discovered 13 sites that have hundreds of Neolithic artifacts, Xinhua was told Thursday.

The 13 sites, in the city of Guyuan, include tombs, kilns and cave dwellings, human bones, and pottery utensils and fragments of red and black pottery.

"The sites have been linked to the Qijia culture, around 4,000 years ago, which was a transitional period from the Neolithic to the Bronze Age," said Ma Qiang with the Ningxia Regional Institute of Cultural Relics and Archaeology.

"The discoveries at the sites will be used to inform research into the Qijia Culture," he said.

The sites were found during a month-long project. Archaeologists also discovered 10 sites containing artifacts and tombs from the Zhou Dynasty (1046-221 BC), which could be used by researchers concerned with the relationship between ethnic minorities and the Great Wall.

Ma told Xinhua that the team had applied for an excavation license.