Sudan's President Omar al-Bashir on Wednesday appointed a peace envoy to South Sudan, mired in conflict since it won independence from its northern neighbour in 2011.

Former ambassador to Juba, Jamal al-Sheikh, was put in charge of "following the implementation" of the peace deal signed last month by warring South Sudanese parties, Bashir told a gathering of Sudanese diplomats.

"Peace in Sudan cannot be separated from peace in the region, and achieving peace in South Sudan is a big step towards a comprehensive peace," he said.

Civil war in the world's youngest country erupted in December 2013, killing tens of thousands, displacing millions and triggering a regional refugee crisis.

South Sudanese arch-foes President Salva Kiir and rebel chief Riek Machar signed their latest peace deal on September 12 in Ethiopia after talks hosted by Khartoum.

South Sudan gained independence under a peace deal ending a 22-year civil war pitting rebel groups against Khartoum.

But the Darfur region and the states of Blue Nile and South Kordofan, close to oil-rich South Sudan, have continued to see deadly conflict pitting rebel groups against the Sudanese government.

Khartoum accuses Juba of supporting insurgents against it.

A US-funded survey released recently estimated that nearly 400,000 people have been killed in the conflict in South Sudan.