Gunmen in war-ravaged South Sudan have abducted at least 89 boys, some as young as 13, from their school in oil-rich Upper Nile State, the United Nations said yesterday.

The boys were taken while doing their exams and the total number of kidnapped children could be "much higher", the UN Children's Fund (UNICEF) said. No group has claimed responsibility for the abductions and the gunmen's intentions were not clear, though in the past armed groups have forcibly recruited children before major offensives. Conflict has been rife in South Sudan since December 2013 when fighting erupted in capital Juba between soldiers allied to President Salva Kiir and those loyal to his former deputy, Riek Machar.