UN General Secretary Ban Ki Moon has called South Sudan's seizure of Sudan's Hij-leej oil field, illegal.<br /><br />He's also urged both sides to show restraint and withdraw troops from the volatile border region. <br /><br />The Arab League says it will hold an emergency meeting to discuss the escalating violence there.<br /><br />Earlier, Sudan's President Omar Al Bashir threatened war against his Southern neighbour. <br /><br />Al Jazeera's Harriet Martin reports from Khartoum.
