Australia on Saturday returned four sets of indigenous Ainu remains to Japan — more than 80 years since they were sent there for research purposes.

The Japanese government has been stepping up efforts to bring back the remains of the indigenous ethnic group from Hokkaido, which were collected — sometimes by excavating tombs — for studies in anthropology and other fields.

The remains, all skulls, were handed over to representatives of the Japanese government and Ainu-related groups in a ceremony at Melbourne Museum.