South Sudan has accused Sudan of bombing one of its oil facilities, despite recent moves to defuse the conflict between the two countries.
A number of blasts have been heard in South Sudan, with a military official telling the BBC that the Unity oil field was targeted.
The government in Khartoum has so far made no public comments on the claim.
On Friday, South Sudan said it was withdrawing its troops from the disputed Heglig oil field.
Sudan claimed it had regained the area by force.
Heglig is internationally accepted to be part of Sudanese territory - although the precise border is yet to be demarcated.
Other issues dividing the two countries are the transit fees the South should pay Sudan to use its oil pipelines and the status of the province of Abyei.
The escalating fighting and rhetoric between the two sides over the past week has led to fears of all-out war.
US President Barack Obama has urged the presidents in Khartoum and Juba to "have the courage" to return to the negotiating table and resolve their differences peacefully.
South Sudan seceded last July following a 2005 peace deal that ended a two-decade civil war in which more than 1.5 million people died.