LANZHOU, July 26 (Xinhua) -- A project is under construction to upgrade security arrangements for Mogao Grottoes, a world cultural heritage site in Dunhuang of northwestern China's Gansu Province, Dunhuang Research institute confirmed Sunday.

     The project embraces a visual monitoring and audio check system, intrusion sirens, entrance control system, wired telecommunication system, broadcasting system and a security control center.

     The project is one of the four projects under the Mogao Grottos conservation program, which began at the end of last year as the largest of its kind in the history of Dunhuang.

     Ranked as a UNESCO world cultural heritage site in 1987, Mogao Grottoes now has 735 grottoes, more than 2,000 colored statues, and 45,000 square meters of frescos.