Barack Obama, the US president, has urged the leaders of Sudan and South Sudan to stop the fighting between their countries and begin negotiations to settle their disputes.
Obama's comments came a day after Sudan's President Omar al-Bashir said his troops had defeated South Sudanese forces who occupied his country's main oilfield, but added that the battle was not over.
"We know what needs to happen - the government of Sudan must stop its military actions, including aerial bombardments," Obama said in a videotaped message to the people of the two countries.
Bashir dismissed a statement by his southern counterpart Salva Kiir that the troops which had invaded Heglig - which accounts for about 50 per cent of Sudan's oil - had begun withdrawing.
"There is no withdrawal. We beat them by force ... Until now, their people are running," Bashir said at military headquarters.
Bashir also threatened to keep Sudan's oil pipelines closed to the South's crude exports.
Al Jazeera’s Peter Greste, reporting from Bentiu in South Sudan, said that on Friday night Sudan had bombed oilfields in Unity state, north of Bentiu.
"Late last night we heard the thump of what sounded like aerial bombardment. We were up there [at the Unity oilfields] today and found the bomb craters of at least four or five bombs there," he said.
"They didn't do a great deal of damage, but we do understand there was one soldier that was killed in the attack. It really underscores the ongoing levels of tensions."
Al Jazeera’s Zeina Khodr, reporting from Khartoum, said Bashir’s government has continued its tough rhetoric.
"The government is broadcasting footage that main oil installation is under control of its forces," she said.
"They are showing pictures of dead bodies of South Sudanese soldiers, and burned vehicles.
"That is hard to independently confirm because of limited access to journalists."
Border clashes between Sudan and South Sudan escalated last week with waves of air strikes hitting the South, and Juba seizing the Heglig oil hub on April 10.
|In-depth coverage of North-South strife over border
South Sudan, which gained independence last July after voting in a referendum to secede from Sudan, claims it occupied Heglig after it was attacked by the Sudanese army.
It had ignored calls by the international community to pull its troops out, saying it was defending its territorial integrity.
Ban Ki-moon, the UN secretary-general, called the south's seizure of Heglig an "illegal act" and urged the two nations to negotiate to avoid all-out war.
A ruling by the Permanent Court of Arbitration in The Hague in 2009 put Heglig in the Sudan state of Southern Kordofan, which the South now disputes.
The Arab League has said it would hold an emergency meeting over the renewed violence between the two countries.
Ahmed bin Helli, the bloc's deputy secretary-general, said on Thursday that the meeting, requested by Sudan, would bring together the regional bloc's foreign ministers and would be held next week in Cairo, the Egyptian capital.