South Sudan's rebel leader Riek Machar is due to arrive in the capital Juba to resume his position of vice-president. His reinstatement is part of a series of measures contained in a peace deal aimed at ending a civil war that has caused the deaths of thousands and the displacement of more than 2 million people.

Machar, who left Juba when the conflict erupted in 2013, will work with president Salva Kiir to form a unity government. The rebel leader was originally scheduled to arrive on 18 April. His delay was due to "logisitical reasons," according to a spokesman, who refused to give further details.

The leader was staying at rebel military headquarters in Pagak, in South Sudan's Upper Nile state. William Ezekiel, spokesperson for the armed opposition faction The Sudan People's Liberation Movement-in-Opposition (SPLM-IO), explained the plane carrying opposition officials from Pagak to Gambella, Ethiopia, was behind schedule, the Sudan Tribune reported.

It is not yet clear whether the delay was connected to the massacre of hundreds of people in Gambella, for which members of South Sudan's Murle tribe have been blamed.

South Sudan descended into civil war in 2013 when Kiir, from the Dinka ethnic group, fired Machar, from the Nuer group, and his cabinet. The dismissal followed Kiir's decision to replace members of the army and government amid rumours of a coup plot by Machar.

Ethnic-related violence then spread, with militia groups carrying out attacks in villages and areas known to be inhabited by either Dinka or Nuer tribes.

More than 10,000 civilians have so far been killed in the conflict, amid allegations of crimes against humanity committed by both sides, including extra-judicial killings, abductions, rape, torture and use of child soldiers. At least two million people have also been displaced.

Although the two warring factions have signed at least seven peace deals, the violence has continued, and a January report from the African Union blamed both opposing leaders for the ongoing unrest.

South Sudan fresh fighting
A woman and a girl from the Dinka community are pictured next to a soldier in the Sobat Secondary School in Malakal in February 2016 Albert Gonzalez Farran/AFP/Getty Images