North Sudan's government has rejected a call from the U.N. Security Council to pull its troops out of the disputed Abyei region.

On Friday, the Council condemned the north's occupation of Abyei, describing it as a “serious violation” of the 2005 peace deal that ended Sudan's north-south civil war.

The north's foreign minister, Ali Ahmad Karti, responded late Saturday, saying the north cannot be asked to withdraw from Abyei because it is Sudanese territory. He added that the occupation is necessary to maintain security in the area.

Both north and south Sudan claim ownership of Abyei, an oil-rich land on the north-south border.

The north's May 21 seizure of Abyei occurred just a few weeks before south Sudan is to formally declare independence from Khartoum.

The United Nations said Saturday it is investigating reports that U.N. peacekeepers in Abyei stayed in their barracks during the recent north-south fighting. Several U.N. diplomats have criticized the peacekeepers, who come from Zambia, for failing to carry out their mandate, which includes protecting civilians in Abyei.

Witnesses and U.N. officials report widespread destruction of huts and buildings in Abyei's main town since northern forces occupied the area.

The north Sudanese government recently informed the U.N. that it wants the peacekeeping force on its southern border to leave its territory when south Sudan becomes independence.

North and south Sudan fought a 21-year war that ended with the 2005 Comprehensive Peace Agreement.

The south voted to split from the north in a January referendum. Abyei was scheduled to hold a separate referendum on which region to join, but the poll never happened because the sides could not agree on who was eligible to vote.