Former South African President Thabo Mbeki met early this week with South Sudan's President Salva Kiir to discuss tensions in the region.
South Sudan became an independent country in July as part of a peace deal reached in 2005 that ended one of the bloodiest civil wars in modern history. Ethnic skirmishes, disputes over oil and border clashes are threatening the fragile peace, however.
South Sudan's Minister of Information Barnaba Benjamin Marial was quoted by the independent Sudan Tribune as saying Sudan had committed "wanton attacks" on targets across the border in an effort to provoke a reaction.
Both sides were called on by the United Nations to return to the negotiating table alongside African leaders.
For his part, Phillip Aguer, a spokesman for South Sudan's military, urged members of the African Union to "watch Khartoum's actions at the border."
The United Nations estimates thousands of people have been displaced by simmering conflict in the region.