The detention of South Sudan?s First Vice-President Riek Machar has effectively collapsed the 2018 peace deal that ended the country?s five-year civil war, his party has said.

An armed convoy led by top security officials, including the defence minister, entered Machar?s residence in the capital, Juba, and disarmed his bodyguards late on Wednesday, said the Sudan People?s Liberation Movement In Opposition (SPLM/IO).

Machar was detained alongside his wife Angelina Teny, who is the country?s interior minister, the party added.

?The arrest and detention of H.E Dr Riek Machar effectively brings the [peace] agreement to a collapse,? said SPLM/IO deputy leader Oyet Nathaniel Pierino.

The government is yet to comment on Machar?s reported house-arrest.

Addressing religious leaders on Wednesday, President Salva Kiir said ?he will never return the country to war?.

The UN has been warning that South Sudan is on the brink of a return to civil war following an escalation of conflict between Machar and the president that has been building for weeks.

The two leaders agreed in August 2018 to end the civil war that killed nearly 400,000 people. But over the last seven years their relationship has become increasingly strained amid ethnic tensions and sporadic violence.

In a press conference on Thursday, Pierino said Machar?s detention had ?abrogated? ? or breached ? the fragile peace deal.

?The prospect for peace and stability in South Sudan has now been put into serious jeopardy,? he added.

A similar warning was issued by the UN Mission in South Sudan (Unmiss), saying the country?s leaders ?stand on the brink of relapsing into widespread conflict?.

Tension remains high in Juba with a heavy military presence reported around Machar?s home.

?There is a high chance of full-scale war but it will be more deadly and more violent because of [the need] for revenge,? one resident told the AFP news agency.

But Pierino called on SPLM/IO members and the public to remain calm as diplomatic efforts continue to resolve the situation.

Reath Muoch Tang, chairman of the party?s foreign relations committee, said Machar was under house-arrest, but that security officials initially tried to take him away.

?An arrest warrant was delivered to him under unclear charges,? Tang said in a statement, calling the action a ?blatant violation of the constitution and the Revitalized Peace Agreement?.

Unmiss warned that the world?s newest nation risked losing the ?hard-won gains of the past seven years? if it returned to ?a state of war?.

?Tonight, the country?s leaders stand on the brink of relapsing into widespread conflict,? the mission said in a statement on Wednesday.

Violations of the 2018 peace deal ?will not only devastate South Sudan but also affect the entire region,? it added.

The British and US embassies have scaled down their diplomatic staff and urged their citizens to leave the country while the Norwegian and German embassies have closed their operations in Juba.

The US has called on President Kiir to free his rival from the reported house-arrest, urging the two leaders to show commitment to peace.

?We urge President Kiir to reverse this action & prevent further escalation of the situation,? the US Bureau of African Affairs wrote on X.

The escalating tensions come amid renewed clashes between forces loyal to the two rivals in the northern town of Nasir in the oil-rich Upper Nile State. (BBC)

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