South Sudanese President Salva Kiir has sacked his foreign minister, less than a week after dismissing the defence and interior ministers.
No explanation was given for the dismissal of Mayiik Ayii Deng, which was announced in a decree on the state television.
The sacked minister is an ally of Mr Kiir, and previously served as the minister in the president's office.
Last week’s sackings have threatened to derail a peace deal with opposition leader First Vice-President Riek Machar.
The opposition called for the reinstatement of Angelina Teny, who Mr Kiir dismissed as defence minister and handed the position to his party. Mrs Teny is also Mr Machar’s wife.
The UN called for the parties to "exercise restraint and engage in a collegial spirit in order to resolve such sensitive national issues”.