Sudan has declared a state of emergency along its border with South Sudan, in a move that imposes a trade embargo on the South and suspends the constitution, SUNA, the official news agency, said.

It said President Omar al-Bashir issued a resolution on Sunday declaring the emergency in border districts of South Kordofan state, White Nile and Sennar states.

The measure follows a month of border fighting with South Sudan, which seceded last July after a peace deal ended one of Africa’s longest civil wars, which killed about two million people between 1983 and 2005.

An emergency has already been in effect for almost a decade in Darfur, along the western border with South Sudan, while a similar status took effect in Blue Nile state last September when an ethnic insurgency began.

Trade across the border has unofficially been banned since South Sudan’s independence, but the emergency formalises that prohibition.

Bashir’s resolution “gives the right to the president and anyone with his mandate” to establish special courts, in consultation with the chief justice, SUNA said.

The state news agency also reported that the governor of White Nile state on the border has set a one-week deadline for 12,000 ethnic South Sudanese, who are gathered south of Khartoum, to leave the country.

“The wali (governor) of White Nile state, Yusuf al-Shambali, confirmed that he has set May 5 as the deadline for the Southerners waiting in Kosti,” a way-station south of Khartoum, it said.

“The presence of Southerners in Kosti threatens the security and the environment for Kosti citizens,” he said.

Foreigners arrested

Meanwhile, a South African demining company on Sunday said two of its workers were abducted by the Sudanese military while on a UN landmine clearance contract in South Sudan.

Ashley Williams, CEO of state-owned Mechem, said its employees, a South African and a local South Sudanese, were seized along with a British UN employee and a Norwegian.

Al Jazeera’s Imran Khan reports on Sudan’s arrest of four foreigners in the Heglig oilfield area

Williams rejected suggestions by the Sudanese army spokesman that the men were working in support of South Sudan in its “aggression” against the north.

“It’s humanitarian work so the story of them being military advisers and this type of thing is completely and utterly nonsense and not true,” he said.

“We are doing humanitarian landmine clearance on a UN contract and our members have full UN immunity. The abduction took place well within South Sudan territory,” the spokesman told the AFP news agency, saying the group was travelling south between two UN bases.

“Then they grabbed them and drove back to Heglig with them where they then said they’ve arrested them in this disputed area while they weren’t there at all.”

A team remained in the area, which the United Nations would bring out with protection over fears of similar action, Williams said.

Sudanese army spokesman Sawarmi Khaled Saad said on Saturday the four were captured within Sudan’s borders in the tense Heglig oil area.

“This confirms what we said before, ‘that South Sudan in its aggression against Heglig was supported by foreign experts,'” he told reporters after the men were flown to the capital Khartoum.