The South Sudanese leader arrived in the Vatican on Friday on the invitation of the pope for talks on bilateral relations with Juba.
President Kiir was accorded a warm reception at the holy land.
He held one-on-one talks and prayer sessions with Pope Francis during which the South Sudanese leader extended an official invitation to the pontiff to visit and hold peace prayers in South Sudan.
The pope vowed to hold prayers for South Sudan at the Vatican before visiting the world’s newest country where tens of thousands have died and over two million have been displaced since the conflict began in December 2013.