A South Sudanese army general resigned on Saturday, citing cases of ethnic cleansing and crimes committed against civilians by the Sudan People's Liberation Army (SPLA).
In a letter addressed to South Sudanese President Salva Kiir, lieutenant general Thomas Cirillo Swaka said he resigned after losing faith in Kiir and the army command.
"I am dissatisfied, and I have lost patience with the conduct of the commander-in-chief and other senior officers at the headquarters of the SPLA as well as unit commanders," Swaka, the army's deputy chief of logistics, said in the letter seen by dpa.
Swaka alleges that a 2013 military conflict was carefully planned and executed, which stands in contrast to the widely held view that violence erupted unexpectedly, in response to a political disagreement between Kiir and his former vice president Riek Machar.
The conflict was bolstered by "tribal militias loyal to President Kiir," according to Swaka.
South Sudan was plunged into a military conflict when a split between Kiir and his former deputy Machar escalated in December 2013. The formation of a unity government did not stop the fighting.
The conflict was fought mainly between the east African nation's two biggest ethnic groups - the Dinka, to which Kiir belongs, and the Nuer, of which Machar is a member.
On Friday, the UN Refugee Agency (UNHCR) said the number of people who have fled South Sudan's civil war has crossed 1.5 million, in what is now the world's third-biggest refugee crisis after Syria and Afghanistan.