US President Barack Obama on Monday appealed for calm in the Central African Republic and for the arrests of those behind the surge of sectarian violence, in an audio message to the country. Obama said Muslim and Christian leaders "are calling for calm and peace. I call on the transitional government to join these voices and to arrest those who are committing crimes," Ben Rhodes, a deputy national security advisor said on Air Force One as Obama flew to South Africa for Nelson Mandela's memorial service