XINING, Dec. 11 (Xinhua) -- Two cliff paintings featuring images of human faces and over 100 tower-shaped cliff paintings have been discovered in the Tongtian River basin in northwest China's Qinghai Province, local authorities said Wednesday.

They are engraved in a mountain located about 600 meters from the river in the source region of the Yangtze River in Yushu Tibetan Autonomous Prefecture.

The paintings of human faces are round-shaped and measure about 30 cm and 35 to 40 cm in diameter, respectively.

"It was the first recorded discovery over the past five years of cliff painting featuring human faces in this area," said Jamyang Nyima, head of the Yushu research institute of history and culture. The date of these paintings has not yet been determined.

He added that the findings will help with studies of human history, art, culture and religion on the ancient Qinghai-Tibet Plateau.

So far, 3,400 cliff paintings have been discovered in 59 sites along the Tongtian River, which feature images including vehicles, animals and symbols.