South Sudan's powerful ex-army chief on Monday announced the formation of a rebel movement to "arrest the carnage" in the country, saying President Salva Kiir could not be trusted to lead the nation to peace.Paul Malong, a hardline ethnic nationalist who fled into exile a few months after Kiir sacked him last year, was sanctioned by the United Nations and European Union for orchestrating the more than four year civil war which has killed tens of thousands and displaced millions.He slammed the ongoing fighting and misery in the world's youngest nation, accusing Kiir of "looting" South Sudan into bankruptcy and turning it into a failed state.Malong said in a statement that his new movement, the South Sudan United Front (SS-UF) "is a just and urgent call ... a struggle to first arrest the carnage that has befell our country and secondly to steer us towards democracy and development."He described the movement as an "army" and himself as its "commander-in-chief", while also calling for democracy, development and peace.Malong said his movement would join the South Sudan Opposition Alliance (SSOA) - a coalition of armed groups which formed in December after a short-lived ceasefire deal was struck with government.Malong was appointed army chief in January 2014, tasked with crushing former vice president Riek Machar's rebel group a month after conflict broke out after Kiir accused Machar of plotting a coup.He was sacked in May last year, and held under house arrest. Once released he went to Kenya on a medical visit and never returned, prompting Kiir to declare him a rebel and accuse his loyalists of waging attacks against government."Malong has confirmed what we have been saying from the day he left Juba," the capital, said presidential spokesman Ateny Wek Ateny."We have said time and again Malong is a rebel. This is what he has been working for."KEEP UPDATED on the latest news from around the continent by subscribing to our FREE newsletter, Hello Africa.FOLLOW News24 Africa on Twitter and Facebook. An ethnic Dinka, like Kiir, Malong retains significant support in his community.Initially pitting the Dinka and Machar's Nuer against each other, South Sudan's conflict has metastasised,drawing in a variety of ethnic groups and grievances.Malong said the SS-UF plans to take part in ongoing talks in Addis Ababa later this month to revive a collapsed peace agreement.