There are tentative hopes for peace in South Sudan after the rebel leader Riek Machar was sworn in as vice president of the world's newest country. His place in a new unity government led by president Salva Kiir is hoped to usher in an end to conflict sparked by Kiir's sacking of Macha as his deputy more than two years ago.

The violence pitted Kiir's dominant Dinkas against Machar's Nuer and left tens of thousands dead and two million homeless.

UN Secretary General Ban Ki-moon welcomed Machar's return to Juba and in a statement said: "The Secretary-General calls for the immediate formation of the Transitional Government of National Unity."

President Kiir spoke of "peace and reconciliation" after Machar was sworn in, telling reporters: "Now that Dr Riek has taken the oath of the first vice president, we will immediately proceed with the establishment of the transitional government of national unity," Reuters reported.

The arrival of Machar, who denied claims he was plotting a coup, had been continually postponed since a peace agreement of August 2015.

One South Sudanese official told IBTimes UK earlier in April that the prospects of peace would be impacted by further any delays.

Machar told reporters: "I hope that with my arrival we shall finish with the obstacles and get into the implementation of the government.

"There are challenges that we need to overcome. The first challenge is the stabilization of the security situation of the country. The second is the challenge is the stabilization of the economy," Reuters reported.