A human rights group appealed to the United Nations on Monday to investigate allegations China’s government is committing crimes against humanity in the Xinjiang region.

Human Rights Watch cited reports of the mass detention of Muslims, a crackdown on religious practices and other measures against minorities in the northwestern region. It said they amount to crimes against humanity as defined by the treaty that established the International Criminal Court.

China is not a member of the court and could use its veto power as a permanent UN Security Council member to block action against Chinese officials, Human Rights Watch said in a report. However, the group said the UN Human Rights Commission should create a body to investigate the charges, identify those responsible and provide a road map to hold them accountable.

More than 1 million people have been confined to camps in Xinjiang, according to foreign governments and researchers. Authorities there are accused of imposing forced labor and birth controls.

The Chinese government rejects complaints of abuses, saying the camps are for job training to support economic development and combat radicalism. The government is pressing foreign clothing and shoe brands to reverse decisions to stop using cotton from Xinjiang due to reports of possible forced labour there.