Sudan's president, who is wanted by the International Criminal Court for alleged war crimes, is expected to visit Uganda on Sunday at the invitation of Uganda's government.

As a signatory to the treaty that created the ICC, Uganda has an obligation to arrest Omar al-Bashir. But Ugandan presidential spokesman Don Wanyama says al-Bashir, who is wanted over alleged atrocities in the Darfur region, is immune from arrest as a head of state.

The reason for al-Bashir's latest visit to Uganda is not immediately clear.

Ugandan President Yoweri Museveni has led criticism of the ICC, calling it "useless" during his inauguration in May 2016, an event that al-Bashir attended.

Some African countries have urged a mass exit from the treaty that created the ICC, saying the court unfairly targets Africans.