South Sudan's First Vice-President Riek Machar, a long-time rival of the country's President Salva Kiir, has been placed under house arrest, his party says.
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).
"Technically, Dr Machar is under house arrest, but the security officials initially tried to take him away," said Reath Muoch Tang, chairman of the party's foreign relations committee.
The government is yet to comment.
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 a five-year 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.
The SPLM/IO said Machar was detained alongside his wife Angelina Teny, who is also the country's interior minister.
"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".
The UN mission in South Sudan has warned that the the world's newest nation risked losing the "hard-won gains of the past seven years" if it returned to "a state of war", following reports of Machar's detention.
