Juba said its armed forces could retaliate if Sudan made further assaults, raising the prospect of a return to the fighting which the United Nations and the African Union are seeking to prevent.
The two armies fought in border skirmishes last month after disputes over oil exports and border demarcation boiled over, following South Sudan’s birth as an independent nation in July.
The attacks on Monday and Tuesday targeted the area of Werguet, some 30 km (19 miles) inside South Sudan’s territory in Northern Bahr Al Ghazal state, officials told a news conference.
Sudan’s army spokesman, al-Sawarmi Khalid, could not be reached on his mobile phone. There was no immediate independent confirmation of South Sudan’s allegations, and limited access to remote border areas makes such verification difficult.
South Sudanese Information Minister Barnaba Marial Benjamin said Sudan’s “acts of aggression” violated a May 2 resolution by the U.N. Security Council which ordered both sides to cease hostilities and settle their differences through negotiations or face sanctions.
Juba has accused Sudan of other attacks since May 2.
“This is a slap in the face of the United Nations and the African Union,” Benjamin said. He noted that the attacks happened as an AU mediator, former South African President Thabo Mbeki, was trying to restart direct talks between the two feuding neighbours.
South Sudan said it remained committed to the peace process but would defend itself if attacked.
“Should we be forced to respond, we should not be blamed,” Benjamin said.
Mbeki, who held talks in Juba on Monday with South Sudanese leaders, had said he believed a date to re-start talks between the two sides could be agreed this week.
Sudan has said it wants a lasting peace with its southern neighbour but insists security issues should be resolved first, specifically that South Sudan should end support for rebels in Sudan’s borderlands.
The South Sudanese government denies providing support to the insurgents.