South Sudan accused its neighbour Sudan of bombing its troops as they pulled out of the disputed oil region of Heglig on Saturday, dampening already faint hopes of any imminent settlement between the bitter foes.
The newly-independent South seized Heglig last week, raising fears of an all-out war with Sudan, then announced it had started withdrawing on Friday, following sharp criticism from U.N. Secretary-General Ban Ki-moon.
The Sudan armed forced bombed our positions last night ... and this morning with Antonovs, South Sudan's army spokesman Philip Aguer told Reuters.
Last night we were in full control of Heglig and now we have almost completed our orderly withdrawal, he added.
There was no immediate response from Sudan's army which said on Friday it had liberated Heglig by force.
Tensions have been rising since South Sudan split away from Sudan as an independent country in July, under the terms of a 2005 deal, taking with it most of the country's known oil reserves.
The countries are still at loggerheads over the position of their shared border and other disputes have already halted nearly all the oil production that underpins both economies.
In Bentiu, a major town on the South's side of the border, about two hours' drive away from Heglig, a long queue of military trucks could be seen. A group of wounded soldiers sat on beds outside a hospital packed with patients.
South Sudan secured its independence in a referendum promised in the 2005 peace accord that ended decades of civil war between Khartoum and the south. Religion, ethnicity and oil fuelled that conflict that killed about 2 million people.
The recent tensions between Sudan and South Sudan have been fuelled by a dispute over how much the landlocked South should pay to export oil via pipelines and other infrastructure in Sudan.
Juba shut down its roughly 350,000 barrel-a-day output in January, accusing Sudan of seizing some of its crude. Oil accounted for about 98 percent of the South's state revenues.
Limited access to the remote border conflict areas makes it difficult to verify the often contradicting statements from both sides.
(Reporting by Hereward Holland, Alexander Dziadosz and Ulf Laessing; Writing by Ulf Laessing; Editing by Andrew Heavens)