Troops linked to north and south Sudan have taken up new positions in the contested Abyei region, according to satellite monitoring, raising fears of an escalation of violence in the area.
Analysts say fertile and oil-producing Abyei is one of the most likely places for conflict to erupt in Sudan as the country prepares for the secession of the south, due to take place on 9 July.
More than 100 people died in clashes between groups aligned to either side last week, a spokesman for the southern army said.
Residents of the Abyei border region were promised their own vote on whether to join the north or south on the same day.
But that vote never took place because of disagreement between the northern Arab Misseriya nomads and the south-linked Dinka Ngok group over who was qualified to vote.