The top UN human-rightsofficial arrived in South Sudan on Monday, officials said, amid mounting global outrage over a wave of atrocities in the world’s newest country.U.N. High Commissioner for Human Rights Navi Pillay and U.N. special envoy forgenocide prevention Adama Dieng arrived in the capital, Juba, U.N. Mission in SouthSudan (UNMISS) spokesman Joe Contreras said.The two officials are expected to remain in South Sudan until Wednesday and holdmeetings with President Salva Kiir and other senior officials. They are scheduled totour massacre sites “if security conditions allow,” Contreras told reporters.