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.

JUBA, March 27 (Xinhua) -- 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.

"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 UNMISS, said in a statement.

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

"This will not only devastate South Sudan but also affect the entire region," he warned in the statement issued Wednesday night.

Haysom called on the parties to immediately cease hostilities and engage in constructive dialogue that puts the best interests of their people at the forefront of this pivotal moment for the country.

"Tonight, the country's leaders stand on the brink of relapsing into widespread conflict or taking the country forward toward peace, recovery, and democracy in the spirit of the consensus that was reached in 2018 when they signed and committed to implementing a Revitalized Peace Agreement," he said.

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 as a violation of the 2018 peace agreement that formed the unity government.

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 on Wednesday night.

He said the arrest was a "blatant" violation of the constitution and the Revitalized Peace Agreement, as no legal procedures, such as lifting his immunity, were followed.

Earlier on Wednesday, UNMISS, in a separate statement, called for an immediate cessation of hostilities and urgent dialogue between the country's leaders to de-escalate tensions and restore calm.

In the previous 24 hours, clashes have reportedly taken place between the South Sudan People's Defense Forces (SSPDF) and the Sudan People's Liberation Movement/Army-in-Opposition (SPLM/A-IO) near Juba, according to the UN.

"We encourage the president and first vice president to lead efforts to prevent further military confrontation and restore calm by meeting to resolve differences and making a joint public statement reassuring all South Sudanese of their shared commitment to peace," Haysom said.

The UN mission said the situation in Upper Nile State also remains volatile, with reports of further mobilization of armed forces and aerial bombardment of civilian areas, allegedly using devices containing a highly flammable liquid that acts as an accelerant on explosion, causing significant casualties and horrific injuries.

UNMISS added that intensive diplomatic efforts are underway to broker a peaceful solution.

South Sudan, which became independent in 2011, signed a peace deal in 2018 that ended a civil war between forces loyal to President Salva Kiir and Machar. Nearly 400,000 people died in the civil war.

Relations between Kiir and Machar, who have dominated South Sudan's politics for decades, remain strained. The clashes and latest political tensions between the two leaders have unsettled many citizens and the international community.