French prosecutors have opened an investigation into four fashion retailers, including a unit of Japan's Fast Retailing, on suspicion of concealing crimes against humanity in China's Xinjiang region, a judicial source said Thursday.

The procedure is linked to accusations against China over its treatment of minority Muslim Uyghurs in the region such as the use of forced labor, the source said.

The source said that Uniqlo France, Zara owner Inditex, France's SMCP and Skechers were the subject of the investigation, confirming a report by French media website Mediapart.