State media say researchers identified more than 2,000 pictorial symbols dating back 8,000 years, on cliff faces in the north-west of the country.

They say many of these symbols bear a strong resemblance to later forms of ancient Chinese characters.

Scholars had thought Chinese symbols came into use about 4,500 years ago.

The Damaidi carvings, first discovered in the 1980s, cover 15 sq km (5.8 square miles) and feature more than 8,000 individual figures including the sun, moon, stars, gods and scenes of hunting or grazing.

"We have found some symbols shaped like both pictures and characters," Li Xiangshi, a cliff carving expert at the North University of Nationalities in Ningxia Hui autonomous region, told Xinhua news agency.

"The pictographs are similar to the ancient hieroglyphs of Chinese characters and many can be identified as ancient characters."

Until the discovery, the earliest characters included 4,500-year-old inscriptions on pottery from Henan province in central China.