DUNHUANG, Gansu - The administration of the Mogao Grottoes, a UNESCO World Heritage Site in Northwest China's Gansu province, is to introduce new measures to control visitor flows and prevent damage to the caves' Buddhist frescoes.

A stricter mechanism will be introduced in 2014 to control daily tourist volumes at the 1,600-year-old caves located southeast of Dunhuang City, announced the Dunhuang Academy, the site's administrator, on Friday.

The new rules will require all individual tourists to make a phone or online reservation before visiting the Buddhist shrine, said Fan Jinshi, head of the Dunhuang Academy.

And the maximum time tourists are allowed to spend in each cave will be shortened from the current eight minutes to five.

Before entering, however, they will be shown a film on the grottoes' history and culture, revealing information formerly left to guides to cover once in the caves, a practice that ate up precious time on site.

"The film can cut short the on-site explaining by tourist guides, so visitors can spend less time in the grottoes but still get a full understanding of the site," according to Fan.

The academy head said the move is to curb excessive volumes of tourists, which is responsible for constant changes in the caves' temperature, humidity and carbon dioxide density that can damage their paintings and sculptures.

According to Dunhuang Academy, the grottoes handled 800,000 tourists last year, and received more tourists than the recommended daily capacity of 3,000 people on more than 100 days in 2012.

The Mogao Grottoes have gained global recognition for their huge collection of Buddhist artworks -- more than 2,000 colored sculptures and 45,000 square meters of frescoes in 735 caves carved along a cliff by ancient worshippers. It became China's first UNESCO World Heritage Site in 1987.