Sudan has declared a state of emergency in areas bordering South Sudan, after weeks of clashes over disputed territory and control of oil resources.
The move is further heightening tensions, as concerns mount of an all-out war.
The current problems began earlier this month when South Sudan occupied the Heglig oilfield.
Sudan, which claims the area, says it has since recaptured it.
South Sudan has been swelling its troop numbers at the border.
It split from Sudan last year as part of a peace deal that ended more than 20 years of civil war.
However, with the unresolved issues of border demarcation and ownership of oil resources, there is no sign of peace in the troubled region.