Sudan has arrested four foreigners and flown them to its capital, accusing the men of illegally entering a border area to help its enemy South Sudan.
The Briton, Norwegian, South African and South Sudanese national taken to Khartoum are said to include staff members of the UN and a Norwegian NGO.
Sudan says they were detained in the disputed oil region of Heglig, in vehicles containing military equipment.
Heglig is the scene of recent fighting betweeen Sudan and its southern neighbour.
The South denies the foreigners were helping its forces and says they were in a UN vehicle that got lost in the area.
After decades of civil war, South Sudan split from Sudan last July, under a 2005 peace deal, taking with it most of the country’s known oil reserves.