Back to civil war? Fighting rocks South Sudan capital

South Sudan, which five years ago celebrated its independence, is enduring a fifth day of violence despite calls for calm by rival leaders. How much of a handle do Salva Kiir and Riek Machar have on their forces, which are once again targeting civilians? And after claims of a government tank firing on a Chinese armoured personnel carrier, killing two peacekeepers, what reaction should we expect from the UN and China?