Omar al-Bashir says South Sudan not ready for split
Sudan President Omar al-Bashir has warned that Southern Sudan will face instability if it votes to secede from the north in the upcoming referendum.
He told al-Jazeera TV the south did not have the ability to create a stable state or provide for its citizens.
Correspondents say the comments will infuriate the SPLM - former rebels who have ruled the south since the two-decades-long civil war ended in 2005.
Later, an attack by gunmen on Southern Sudan's military left four people dead.
Col Philip Aguer, a military spokesman, told the Associated Press that forces loyal to rebel leader Gatluak Gai had attacked forces in the Sudan People's Liberation Army overnight in the oil-rich area of Unity state.
He said the SPLA troops had retaliated and killed four of the rebels.
UN officials confirmed that they had received reports of an attack in the area, but did not say which side had suffered the fatalities.
Correspondents expect an overwhelming "yes" vote in the referendum, which would see the world's newest country come into being.
The poll, which begins on Sunday, was part of the terms of the 2005 Comprehensive Peace Agreement (CPA), which ended the civil war.
In an interview with the Arabic news channel al-Jazeera, Mr Bashir said he understood why many southerners wanted independence, but he expressed concern at how the new nation would cope.
"The south suffers from many problems," he said.
"It's been at war since 1959. The south does not have the ability to provide for its citizens or create a state or authority."
Mr Bashir said southerners living in the north would not be allowed dual citizenship, and floated the idea of the two nations joining in an EU-style bloc.
He also raised the issue of Abyei, an oil-rich region with disputed borders.
He warned that if southerners seized the region for themselves, it could lead to war.
Analysts say Mr Bashir is under intense pressure from northern politicians, who fear that secession of the south may lead to a further splintering of the country.
North and south Sudan have suffered decades of infighting in conflicts driven by religious and ethnic divides.
Southerners have long complained of mistreatment at the hands of the Khartoum government.
At an event on Friday, former South African President Thabo Mbeki - the African Union's mediator on Sudan - said the vote marks the "true emancipation" of the people of the south.
"The work of freedom is just at its beginning. We are confident that the southern Sudanese people have the strength and spirit to succeed in that endeavour," he told a large crowd in Juba, the south's capital.
Southern Sudanese will have a week to cast their vote on the future of the region, one of the least developed areas in the world.
Turnout will be important because the CPA stipulates a quorum of 60% of the 3.8 million registered voters.
Both Sudan and the South are reliant on their oil revenues, which account for 98% of South Sudan's budget. But the two countries cannot agree how to divide the oil wealth of the former united state. Some 75% of the oil lies in the South but all the pipelines run north. It is feared that disputes over oil could lead the two neighbours to return to war.
Although they were united for many years, the two Sudans were always very different. The great divide is visible even from space, as this Nasa satellite image shows. The northern states are a blanket of desert, broken only by the fertile Nile corridor. South Sudan is covered by green swathes of grassland, swamps and tropical forest.
Sudan's arid north is mainly home to Arabic-speaking Muslims. But in South Sudan there is no dominant culture. The Dinkas and the Nuers are the largest of more than 200 ethnic groups, each with its own languages and traditional beliefs, alongside Christianity and Islam.
The health inequalities in Sudan are illustrated by infant mortality rates. In South Sudan, one in 10 children die before their first birthday. Whereas in the more developed northern states, such as Gezira and White Nile, half of those children would be expected to survive.
The gulf in water resources between north and south is stark. In Khartoum, River Nile, and Gezira states, two-thirds of people have access to piped drinking water and pit latrines. In the south, boreholes and unprotected wells are the main drinking sources. More than 80% of southerners have no toilet facilities whatsoever.
Throughout the two Sudans, access to primary school education is strongly linked to household earnings. In the poorest parts of the south, less than 1% of children finish primary school. Whereas in the wealthier north, up to 50% of children complete primary level education.
Conflict and poverty are the main causes of food insecurity in both countries. In Sudan, many of the residents of war-affected Darfur and the border states of Blue Nile and South Kordofan, depend on food aid. The UN said about 2.8m people in South Sudan would require food aid in 2013. The northern states tend to be wealthier, more urbanised and less reliant on agriculture.