New Delhi, April 14 -- The U.N. has expressed concern over violence in the strategic town of Akobo in South Sudan' s Jonglei State, which was retaken by opposition forces after they ousted government troops.

Fighting started over the weekend and the Sudan People's Liberation Army-in-Opposition spokesman Lam Paul Gabriel said on Monday that opposition fighters captured the town and took military vehicles and weapons. Government troops, which seized the town in March, withdrew.

The public service minister, Ezekiel Lol Gatkuoth, called the attacks "senseless and unjustified," saying the opposition forces had put civilians in harm's way. He said the army would provide more details on what transpired, but the army spokesperson refused to com...