U.N. officials told Reuters the world body was moving peacekeepers to hotspot areas to create limited buffer zones because of fears that conflict may erupt in the build-up to a referendum on whether the south should declare independence or stay in Sudan.

"The remarks ... on the deployment of a U.N. buffer zone on the border between north and south reflect nothing but ignorance of the facts on the course of events in Sudan or harassment aimed at (Sudan's) stability and integrity," Sudan's army spokesman told the state Suna news agency late on Friday.

People from Sudan's oil-producing south are now less than three months away from the scheduled start of the vote, promised in a 2005 peace deal that ended decades of north-south civil war -- a conflict that left an estimated 2 million dead.

Southerners, who mostly follow traditional beliefs and Christianity, are widely expected to vote for secession, while the largely Muslim north wants to keep Africa's largest country united.

The president of the semi-autonomous south, Salva Kiir, last week told visiting U.N. Security Council envoys he feared the north was moving troops southwards and preparing for war, members of the delegation said.

Washington's ambassador to the United Nations, Susan Rice, on Thursday confirmed Kiir had asked for a U.N.-administered 10-mile (16-km) buffer zone along the ill-defined border. U.S. President Barack Obama last week said Sudan was one of his top priorities, adding he wanted to prevent war and avert the risk of conflict opening up a new space for terrorist activity in the region.

Army spokesman Al-Sawarmi Khaled told Suna on Friday there was no threat to southerners' safety and that Sudan's armed forces could deal with any security incidents. He added the U.N. peacekeepers in the country already had their own job to do, monitoring the roll out of the 2005 peace accord.