Sudan has reportedly declared a state of emergency along its border with South Sudan after weeks of clashes.
The decree will apply in the border districts of the South Kordofan, White Nile and Sennar states, according to the state-run Suna news agency.
Meanwhile, South Sudan has said it is willing to pull its police forces out of the disputed Abyei border region.
The current clashes began earlier this month when South Sudan occupied the Heglig oilfield area for 10 days.
The state of emergency "gives the right to the president and anyone with his mandate" to establish special courts, in consultation with the chief justice, according to Suna.
There were fresh skirmishes between the two countries' forces on Sunday, reports the BBC's Andrew Harding from the Sudan-South Sudan border.
South Sudanese forces fired at helicopter gunships, prompting Sudanese artillery to respond, our correspondent says.
South Sudanese authorities have meanwhile informed the United Nations that it is prepared to withdraw police forces from the disputed region of Abyei.
"The minister of interior will enhance the withdrawal of South Sudan's police force from Abyei... as long as the UN and African Union will look after its citizens in the area", a South Sudanese spokesman told AFP news agency.
'Abduction'Also on Sunday, a South African de-mining company said two of its employees, who were among four foreigners detained by Sudanese forces on Saturday, were there for "humanitarian work".
"We are doing... landmine clearance on a UN contract and our members have full UN immunity. The abduction took place well within South Sudan territory," Ashley Williams, CEO of state-owned Mechem, told AFP.
The four - from the UK, Norway, South Africa and South Sudan - have been flown to the Sudanese capital Khartoum for "further investigations".
Sudanese officials insist the men were aiding South Sudan, a charge rejected by the South.
Tension between the countries has been rising since the Heglig oilfield was occupied by forces from South Sudan earlier this month.
They left about a week ago, after holding the area for 10 days.
Sudan has been accused of carrying out a number of air raids on South Sudan this week. It denies the charges.
South Sudan became independent from Sudan last year after a civil war that lasted two decades and in which an estimated 1.5 million people were killed.
Sudan: A country divided
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. The residents of war-affected Darfur and South Sudan are still greatly dependent on food aid. Far more than in northern states, which tend to be wealthier, more urbanised and less reliant on agriculture.
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