JUBA - South Sudanese First Vice-President Riek Machar was placed under house arrest in the national capital of Juba on Wednesday night as the United Nations mission in the country called for restraint amid rising tensions across the country.

"Following reports tonight of the detention of First Vice-President Riek Machar, the UN Mission in South Sudan (UNMISS) calls on all parties to exercise restraint and uphold the Revitalized Peace Agreement," Nicholas Haysom, special representative of the UN secretary-general to South Sudan and head of the UNMISS, said in a statement issued on Wednesday night.

Haysom said the unilateral amendments by the parties to that agreement, which jeopardize the hard-won gains of the past seven years, risk returning the country to a state of war.

Reath Muoch Tang, acting chairperson of the National Committee on Foreign Relations for the Sudan People's Liberation Movement-in-Opposition (SPLM-IO), condemned the arrest, which he said is a violation of the 2018 peace agreement that formed the unity government.

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Tang said the defense minister and chief of national security were in the convoy that delivered an arrest warrant to Machar, along with more than 20 heavily armed vehicles that forcibly entered his residence.

"His bodyguards were disarmed, and an arrest warrant was delivered to him under unclear charges. Attempts are currently being made to relocate him," Tang said in a statement, terming the arrest a violation of the constitution and the Revitalized Peace Agreement, as no legal procedures, such as lifting his immunity, were followed.

The UNMISS said intensive diplomatic efforts are underway to broker a peaceful solution.