Sudan 'declares emergency' on border with South Sudan

Sudan has 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.

Sudanese local authorities have ordered a group of 12,000 ethnic South Sudanese people to leave Sudan within a week.

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.

Some 12,000 South Sudanese people have been gathering in the border town of Kosti in recent weeks after the Khartoum government told South Sudanese living in the north to either regularise their residency papers or leave the country.

They are part of an estimated 500,000 southerners in the north, who either fled there during the two-decade civil war, or who went to look for work.

As an 8 April deadline passed, thousands of them started their journey home.

They have become stuck at the river port of Kosti as the Khartoum government refuses to allow barges to come up from the south to take them. Meanwhile the regional governor has given them until 5 May to leave.

Khartoum has been demanding guarantees from South Sudan that the barges will not be used to carry military equipment or militia northwards.

The rights of southerners in the north and Sudanese in the South is one of a number of issues still to be resolved since South Sudan became independent last year.

Sharing the oil revenue is the biggest one, which has led the two countries to the brink of all-out conflict.

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 the civil war, in which an estimated 1.5 million people were killed.