Military spokesman Sawarmi Khaled Saad said the Sudan People's Liberation Army, former rebels who became the southern army after a 2005 peace treaty, "concentrated military forces" in the northern White Nile state.
"The referendum will be impossible if these violations continue," he told the Sudanese Media Center, which is close to the country’s intelligence service.
South Sudan spokesmen could not be immediately reached for comment.
Military spokesman Sawarmi Khaled Saad said the Sudan People’s Liberation Army, former rebels who became the southern army after a 2005 peace treaty, "concentrated military forces" in the northern White Nile state.
"The referendum will be impossible if these violations continue," he told the Sudanese Media Center, which is close to the country’s intelligence service.
South Sudan spokesmen could not be immediately reached for comment.
North and south Sudan, which fought a 22-year war that ended in a power-sharing deal and the promise of a referendum, dispute the borders drawn in 1956, when Sudan gained independence from Anglo-Egyptian administration.
One of the points of dispute is the border between Renk County in the southern state of Upper Nile and Jabalain, in the north’s White Nile State.
There is a population of southern Dinka tribesmen who live north of the border, while Arab nomads travel to the south yearly in search of pastures.
The border is one of the most sensitive points of dispute as the south prepares to vote Jan. 9 on whether it will remain in a united Sudan.
Own referendum
A top British diplomat, meanwhile, quoted the region’s president as saying that South Sudan could organize its own referendum on independence if a planned January vote under the auspices of the central government suffers a "huge delay."
Mark Lyall Grant, Britain’s permanent representative to the United Nations, was speaking after visiting U.N. Security Council envoys met south Sudan President Salva Kiir for talks the envoy described as "very frank."
Kiir has repeatedly said the Jan. 9 polling date is "sacrosanct."
He has accused President Omar al-Bashir’s National Congress Party (NCP) of delaying progress on preparations for the vote.
Lyall Grant said Kiir told delegates that "if there was a huge delay by the NCP, then they reserve the right to hold their own referendum."
The delegates from the 15 countries that sit on the council were in the regional capital Juba to discuss preparations for the landmark vote as international concern grows over the risk of renewed conflict.
"The Security Council is united behind pressing both parties to make necessary preparations to tackle the necessary issues, to allow the referenda to take place on time, be credible and be respected," Lyall Grant told reporters.
Economy, social problems and security
The closed door talks lasted for more than two hours, as delegates questioned the south’s leaders on issues including the economy, social problems and security.
The independence vote is to be held across the south and in the disputed oil district of Abyei on the north-south border. Preparations have been seriously delayed.
On Thursday, the envoys met representatives of the Southern Sudan Referendum Commission, the body running the vote. "Those of us who have seen referenda and elections elsewhere in the world do feel that it was a very ambitious timetable," he said.
"The international community will do everything it can to make everything happen," he added.
Most analysts expect voters to opt to break away but there have been no large-scale independent opinion polls.
Southern leaders have previously hinted at the possibility of declaring independence if the planned January referendum were compromised. Under this scenario, a locally organized referendum would be held to legitimize that declaration of independence.
Recovering from war
The grossly underdeveloped south is still recovering from decades of war with the north, during which about two million people were killed in a conflict fuelled by religion, ethnicity, ideology and resources including oil.
"Southern Sudan faces many challenges well beyond that, even if indeed there is separation," Lyall Grant said.
The envoys arrived later in al-Fasher, capital of North Darfur state, where they were met at the airport by about 300 demonstrators chanting in support of Bashir.
"With our blood and our souls we sacrifice ourselves for Bashir," chanted women, who were dressed in white.
Bashir is wanted by the International Criminal Court for alleged war crimes and genocide in Darfur. The delegation, due in Khartoum on Friday, will not meet with the leader, the first sitting head of state to be indicted by the court.
The United Nations says 300,000 people have died in the troubled western region after mostly ethnic rebels revolted against the Khartoum government in 2003.
Bashir’s government denies the charges and says 10,000 people died.