South Sudan plunged into warfare two years after independence from Sudan in 2011 when a political dispute between Kiir and then vice-president Riek Machar erupted into armed confrontation.

A previous peace deal signed in 2015 fell apart a year later after clashes broke out between government forces and rebels.

Machar, leader of the main rebel group the SPLM-IO, and other insurgent factions signed the new agreement with the Juba government on Wednesday after assurances that a power-sharing accord would be honoured. The deal, mediated by Sudan, reinstates Machar to his former role as vice-president.

The stability of South Sudan is also important for Sudan and other neighbouring countries, who fear a new flare up of the conflict could flood them with refugees.

The civil war started in 2013, fuelled by personal and ethnic rivalries. The conflict has killed at least 50,000 people, many of them civilians, according to the United Nations.

An estimated quarter of South Sudan's population of 12 million has been displaced and its economy, which heavily relies on crude oil production, ruined.

The secession of South Sudan also hit Khartoum's economy hard, taking with it most of the region's oil reserves.

Khartoum and Juba agreed in June to repair oil infrastructure facilities destroyed by the war within three months to boost production and said a joint force would be established to protect oilfields from attacks by rebels.

The US, Britain and Norway, known as the Troika which back peace efforts, welcomed the signing of the deal.

"We hope discussions will remain open to those who are not yet convinced of the sustainability of this agreement," they said in a statement. "We must seize this broader regional momentum to secure peace for the people of South Sudan."

Australian Associated Press