South Sudanese authorities have imposed a countrywide dusk-to-dawn curfew after a night of violence during which businesses run by Sudanese traders in the capital were looted.

President Salva Kiir of South Sudan said what happened in Wad Madani was a heinous and "unacceptable" crime. He urged Sudan's government to protect South Sudanese citizens trapped there, and to investigate the killings with the help of international humanitarian organisations.

South Sudan police have enforced a nationwide curfew following deadly riots in Juba over reported killings of South Sudanese in Sudan. Shops have closed as security forces relocate Sudanese citizens for safety.

South Sudan's police imposed a nationwide curfew starting at 6 p.m. (1600 GMT) on Friday after a night of rioting in the capital over the alleged killing of South Sudanese people by the army and allied groups in neighbouring Sudan.