The UN Security Council has condemned Sudan's takeover of the disputed border region of Abyei and demanded the withdrawal of its troops.
The region is also claimed by South Sudan, which is due to become independent from north Sudan in July.
The BBC reports there are fears the Abyei dispute could reignite a civil war.
A Security Council statement said the north's occupation of Abyei was a ''serious violation'' of a peace accord with South Sudan.
Sudanese troops moved into Abyei on 21 May and seized the capital, Abyei.
Attacks in the district have been blamed on northern nomads, the Misseriya, who traditionally graze their cattle there. A southern group, the Dinka Ngok, also claims Abyei.
President Omar al-Bashir has already rejected calls by the United States and the European Union to pull his troops out of Abyei.
The BBC reports Abyei was granted special status under a peace deal in 2005, which ended the civil war after 22 years. A joint administration was set up in 2008 to run the area until a referendum decided its fate.
That vote was due to take place in January, but has now been postponed indefinitely.
