KAMPALA (Reuters) - South Sudan s president has given top jobs to three generals facing U.N. sanctions over alleged violations during a four-year-old civil war. Campaign group Human Rights Watch called the promotions  a slap in the face of justice  - but the presidency said the three men were good officers who had been falsely accused.   In a decree read out on state radio late on Thursday, President Salva Kiir appointed Marial Chanuong as his new head of army operations, training and intelligence, and Santino Deng Wol as the head of ground forces.  Gabriel Jok Riak was named deputy chief of defense.  The U.N. Security Council imposed travel bans and asset freezes on the three and others in 2015. It accused Chanuong of commanding troops who led the slaughter of Nuer civilians in and around (the capital) Juba  in December 2013, including hundreds it said were reportedly buried in mass graves.    I am in my country. I can do anything in my own country,  Chanuong told Reuters Friday. The United Nations said Wol commanded troops who killed children, women and old men during a 2015 offensive, while Riak violated a ceasefire in early 2014.   Kiir s spokesman, Ateny Wek Ateny, said the three generals were  very genuine, obedient commanders  who had been falsely accused. But Human Rights Watch said the announcement, made on the eve of the fourth anniversary of the war s outbreak, showed the impunity enjoyed by commanders accused of abuses.    Having these people nominated to new positions is a slap in the face of justice and a slap in the face of the international community,  the organization s Jonathan Pednault told Reuters. South Sudan plunged into civil war in December 2013 when a political crisis escalated into fighting between forces loyal to Kiir, an ethnic Dinka, and rebels allied with his former deputy Riek Machar, a Nuer.     The conflict has reopened ethnic fault lines and spread across the country, where more than a dozen armed groups are battling for land, resources, revenge, and power amid widespread reports of rape, murder and torture.     Several ceasefires have been agreed but broken. Tens of thousands have been killed since the war broke out.  