South Sudan sees influx of refugees crossing the border
21 December 2011 Last updated at 07:48 GMT
A new country was created in July when South Sudan declared independence and broke away from Sudan, but partition certainly has not ended problems between the two.
They disagree on their shared border and accuse each other of supporting rebels in their territory. The growing division is also causing a humanitarian problem.
BBC's James Copnall travelled to a refugee camp in Mabaan county, on the South Sudan side of the frontier, which has seen a big influx of people in recent weeks.