A South African court has ruled that the government's decision to withdraw from the International Criminal Court was unconstitutional.

A judge in the North Gauteng High Court on Wednesday instructed the government to revoke its notice of withdrawal from the human rights tribunal based in The Hague, Netherlands.

South Africa's main opposition party had gone to court, saying the government's notice was illegal because the South African parliament was not consulted.

South Africa's withdrawal announcement followed a 2015 dispute over a visit by Sudanese President Omar al-Bashir, who is wanted by the ICC for alleged war crimes, crimes against humanity and genocide in Darfur. Al-Bashir was allowed to leave South Africa even though a local court ordered authorities to stop him.