South Sudan's President Salva Kiir has removed the country's military chief and reinstated his predecessor whom Kiir had sacked three months earlier, state-run television announced.

The moves add to relentless turnover within the ranks of South Sudan's military and government as Kiir contends with armed conflict and speculation within the country about his eventual succession.

Kiir, 74, has led a transitional government in the impoverished and fractured nation since independence from Sudan in 2011. Scheduled elections have twice been postponed and First Vice President Riek Machar, Kiir's main rival during a 2013-2018 civil war, was charged last month with treason.

The South Sudan Broadcasting Corporation announced late on Wednesday that Kiir had appointed Paul Nang Majok to replace Dau Aturjong as the new Chief of Defence Forces, without providing a reason for the decision.

Aturjong was reassigned to be a technical adviser at the defence ministry.

In July, Kiir had, without explanation, sacked Majok after seven months in the post and replaced him with Aturjong.

That decision came after renewed fighting in the northeast in which the military was briefly overrun by a militia from Machar's Nuer ethnic group.

The government placed Machar under house arrest in March, accusing him of supporting the militia, and he went on trial for treason, murder and crimes against humanity last month. Machar has denied the allegations.

His detention reignited fears of a return to full-blown civil war, with his supporters accusing the government of violating a 2018 peace and power-sharing agreement.

Analysts say that Kiir's repeated shake-ups of the government and security apparatus are aimed at consolidating his hold on power and keeping various factions satisfied.

UN investigators last month accused South Sudanese leaders of "systematic looting" of the nation's wealth for their personal gain.