JOHANNESBURG - Sudan declared a state of emergency along its Heglig border with South Sudan.
President Omar al-Bashir made the announcement, which imposes a trade embargo on the south and suspends the constitution, on Sunday.
The announcement comes days after South Sudan president Salva Kiir accused the country's northern rival of declaring war by bombing a market and oilfield on Monday.
South Sudan broke away from its neighbour and became independent in July.
The two countries have been unable to resolve disputes over sharing oil revenue and determining a border
Meanwhile, the Department of International Relations and Cooperation on Sunday said it was investigating the circumstances which led to the arrest of a South African man in Sudan.
The Sudanese Defence Ministry confirmed that four foreign nationals, including the South African man, have been flown to the country’s capital Khartoum for questioning.
The four men were arrested by the Sudanese army for allegedly entering an oil-producing field illegally.
It is belived that the group was in Sudan as part of a contract with the United Nations, to help with de-mining.
However, Sudanese authorities are reportedly accusing the men of aiding South Sudan in the ongoing conflict between the two countries.