South Sudan President Salva Kiir will meet his rival Riek Machar in Addis Ababa on Wednesday, as part of talks to try and negotiate an end to a five-year-old civil war, Ethiopia's foreign ministry said.

The ethnically-charged conflict has killed tens of thousands of people in the world's youngest country and repeatedly brought large parts of its population to the brink of famine. A series of ceasefires and pacts have failed.

"The meeting on South Sudan tomorrow will be held under the auspices of (Ethiopian) Prime Minister Abiy Ahmed with the aim of bridging gaps between President Salva Kiir and Riek Machar," the ministry statement said.

Fighting first erupted between troops loyal to Kiir and Machar, then the vice president, in December 2013 - just two years after South Sudan's independence from Sudan.

Machar has been held under house arrest in South Africa since late 2016.

He will be in Addis Ababa on Wednesday, the Ethiopian ministry said. Foreign ministers from the East African bloc IGAD will then discuss South Sudan on Thursday, followed by a leaders' gathering in the Ethiopian capital, the ministry added.