More than 5,300 pieces of ancient Chinese manuscripts have been "returned" from France in digital form and are available online, according to the National Library of China.

The online resources have been provided by France's national library, which holds more than 7,000 original copies of the Dunhuang manuscripts.

The documents, which date from the fifth to 11th centuries, were discovered in the Mogao Grottos in Gansu province in the early 20th century.

There are more than 50,000 of them, including history, linguistics, art and religious documents. Most of the manuscripts are in Chinese, but some are written in other languages such as Khotanese and Hebrew.

Around 16,000 Dunhuang manuscripts are stored at China's National Library, while the rest are scattered overseas in Russia, Britain, France and Japan.

In 1908, French Sinologist Paul Pelliot took 7,000 of the documents to France. They are widely recognized as the most important parts.

China launched a major project to protect ancient books in 2007 and began to investigate and retrieve millions of Chinese classics based overseas. In 2015, China's National Library started a digital cooperation project, using digital content or high-definition print to popularize ancient Chinese works.

According to Lin Shitian, director of the National Center for Preservation and Conservation of Ancient Books, France's national library donated digital documents of the painting series Forty Scenes of Yuanmingyuan, of the Old Summer Palace in Beijing, to China's National Library in 2015, and suggested further cooperation on the Dunhuang relics.

More than 50 volumes of The Yongle Canon, an ancient encyclopedia, were also retrieved in digital form from Harvard University, Oxford University, the British Library and several other organizations overseas, Lin said.

Zhao Wenyou, who works for the same national center as Lin, said unless private collectors donate or sell, most of the hard copies of ancient Chinese books scattered overseas will be hard to retrieve.

"Digitization may bring back ancient works in digital form, which is a more realistic and feasible solution," he said.

According to Zhao, researchers at his center are investigating significant ancient books overseas and setting up bibliographic databases. They are also cooperating with counterparts in other countries to "bring back" precious documents using digitization or photocopying.

"These paper collections are brittle and prone to acid. We have to race against time to do these jobs," he added.

The 5,300 pieces of Dunhuang manuscripts are not just for researchers. The general public can also log onto the website of China's National Library to browse the full text, said Liu Bo, who led the project to retrieve the documents.

"These documents are the window for people from all walks of life to understand and study the history of China. Only in this way can we bring these precious ancient books to life," Liu said.