South Sudan president sacks Upper Nile governor after clashes with ethnic militia

The latest development compounds a confrontation between the two men that started after the White Army militia forced government troops to withdraw from the flashpoint town of Nasir near the Ethiopian border.

In response Kiir's government detained several officials from Machar's party SPLM-IO, including the petroleum minister and the deputy head of the army.

The mounting standoff has fuelled fears that the world's newest nation could slide back into conflict about seven years after it emerged from a civil war that killed hundreds of thousands.

In a decree read on state TV late on Wednesday, Kiir sacked Upper Nile governor James Odhok Oyay who is from SPLM-IO and replaced him with James Koang Chuol, a lieutenant general who hails from Nasir.

Oyay's sacking prompted anger from SPLM-IO which has already partially pulled out of the 2018 peace agreement in protest over the arrests.

The removal of Oyay "constitutes another unilateral action and a severe violation of the Revitalised Peace Agreement," Machar's spokesperson Puok Both Baluang said in a statement, referring to the 2018 pact.

Information Minister Michael Makuei in turn accused Machar's party of jeopardising the peace deal and told Reuters that Oyay was "sacked in order to bring peace" to Upper Nile state.

The government has accused the SPLM-IO of links with the White Army, which mostly comprises armed ethnic Nuer youths who fought alongside Machar's forces in the 2013-2018 war against predominantly ethnic Dinka troops loyal to Kiir. The party denies the allegations.

The fighting around Nasir has already displaced 50,000 people since late February, according to the United Nations which warned this week that the country was "on the brink of relapse into civil war".