North Korea's leader is "begging for war", the US ambassador has said at an emergency meeting of the UN Security Council.

UN Security Council members have called for further sanctions against North Korea after a powerful nuclear test explosion added another layer of urgency for diplomats considering what to do about the North's persistent weapons programmes.

South Sudan's capital was rocked by heavy arms fire between forces loyal to the president and those of the vice president, causing widespread casualties and raising fears the country is returning to civil war.