An archive photo of the disputed border town of Abyei between N.Sudan and Sudan. (Photo: AP)
The United Nations humanitarian agency (OCHA) said in a weekly report monitored Saturday that today's airstrike was the first reported aerial bombing in the Abyei area since last June, when Khartoum and southern officials signed an agreement to demilitarise the area along their disputed border.
Four bombs were dropped on 31 March in Um Khariet, OCHA said in its online report which cited UN peacekeepers based in Abyei. Um Khariet is about 40 kilometres (25 miles) northeast of Abyei town.
OCHA, in its weekly bulletin for Sudan, said humanitarian agencies "are extremely concerned" that the bombing will negatively affect the return of displaced people north of the Bahr Al Arab/Kiir River and the peace process in Abyei.
"The majority of the 110,000 people displaced from Abyei in May 2011 have yet to return and cite the continued presence of armed forces, lack of clarity on the new administration, the destruction of infrastructure, the threat of landmines and lack of livelihoods as the main factors hindering their return," OCHA said.
Abyei, a fertile border district claimed by both Sudan and South Sudan, was to vote on its future in January last year alongside a referendum on independence for the South.
That southern ballot delivered a landslide for secession, and South Sudan gained independence in July after Africa's longest war. Both sides were to keep troops out of Abyei until the vote on its future. But arguments over voter eligibility meant Abyei's plebiscite did not happen, and Khartoum's troops rolled in to expel the south's Sudan People's Liberation Army, sparking global condemnation.
According to a January report by UN chief Ban Ki-moon, Sudanese troops and police remain north of the river, while South Sudanese police are stationed below it. The UN Security Council has demanded that both sides withdraw their forces.
The 31 March air strike occurred during a period of high tension between Sudan and the South, with Sudan alleging a southern troop buildup near oil-rich Heglig to the east of Um Khariet after earlier border clashes between the two nations, and accusations from the South that its border region had been bombed.