Japan said Wednesday it will add the Mozu-Furuichi group of ancient burial grounds in Osaka Prefecture and former gold and silver mines on Niigata Prefecture's Sado Island to its provisional list of sites seeking UNESCO World Heritage registration.

The government expanded the provisional list for the first time in two years, bringing the total number of Japanese cultural asset candidates to 13.

However, while the central government and local authorities in Osaka and Niigata are set to draw up recommendations for the new candidate sites, there is no guarantee that the two newly picked sites will acquire World Heritage status due to competition from many other Japanese sites.

The U.N. Educational, Scientific and Cultural Organization, meanwhile, is refraining from rapidly expanding the World Heritage list.

The Mozu-Furuichi site in southern Osaka comprises some 90 tumuli built between the late fourth and early sixth centuries, including the largest, Daisen Kofun, a nearly 500-meter-long, keyhole-shaped mausoleum. Legend has it that it contains the remains of Emperor Nintoku.

The Sado mines were exploited for more than 400 years starting in the mid-16th century.