KHARTOUM Sudan's army accused South Sudan on Saturday of having troops on its territory, a sign tensions between the former civil war foes were unlikely to cool despite an international ultimatum to end fighting.
Sudanese army spokesman al-Sawarmi Khalid said the military would abide by a U.N.-backed African Union call to halt hostilities, in an effort to end weeks of border fighting that has threatened to escalate into a full-blown war.
But Khalid said the army had a right to defend its territory from foreign troops.
"We have committed to (the decision). And no shot has been fired from our side and no attacks or raids have been launched ... towards South Sudan," Khalid told Reuters.
"But we have to point out that we are still affected by the presence of the South Sudanese army inside our territories in some areas," he said, naming Kafen Debbi and Samaha in south and east Darfur.
South Sudan's army, the SPLA, denied the allegation.
"(Kafen Debbi) was used by ... militia to attack us. And these are inside western Bahr al-Ghazal, which is part of our territory," SPLA spokesman Philip Aguer said.
Fighting along the 1,800 km (1,200 mile) border erupted weeks ago after several rounds of failed talks to resolve disputes over oil revenues, border demarcation and citizenship.
The dispute has been marked by bellicose rhetoric from both sides as well as claims and counter-claims that are difficult to verify because of limited access to the border areas.
Sudan, which was Africa's largest country before the South gained independence in July, sits atop some of the continent's most significant oil resources.
South Sudan has accused the Sudanese army of launching air strikes and ground attacks on its territories over the past weeks, but Sudan has denied these allegations.
The United Nations has condemned the air raids, and on Wednesday the Security Council passed a resolution threatening both sides with sanctions if they failed to comply with the African Union road map to start talks.
"We affirm completely we have no airplanes nor bombardments that have attacked inside South Sudan's territories, even before a month ago. These are just accusations," Khalid said.
SUDAN SAYS HAS RIGHT TO SELF-DEFENCE
Sudan's foreign ministry said in a statement it had informed the African Union and the Security Council of its commitment to halt hostilities with South Sudan.
But if they failed to persuade South Sudanese forces withdraw from Sudanese territory, Sudan's "armed forces will find themselves forced to use self-defense to expel the aggressor forces," the statement said.
Aguer said on Saturday militiamen allied to the Sudanese army had defected after they were ordered to attack an oilfield in the Upper Nile state.
"They changed their mind and joined the SPLA," Aguer said from the southern capital Juba. "They were part of SAF (Sudanese armed forces) and joined us with 250 of their men, 10 vehicles, seven of which were mounted with heavy machineguns."
Khalid denied the allegation.
Sudan lost three-quarters of the oil after Juba's secession under a 2005 deal that ended two decades of civil war between the north and south.
Heglig, an oilfield that the South seized last month before withdrawing under international pressure, provides Sudan with about half of its 115,000 bpd output.
Last month Sudan arrested a Briton, South African and Norwegian, along with a South Sudanese soldier whom authorities said had illegally entered the Heglig area and accused them of being spies for the SPLA. South Sudan believes Heglig is part of its territory.
Khalid said the foreigners were still under investigation.
"Their mere presence in that area is suspicious. That is what led to their arrest," Khalid said.
The United Nations has said the four were carrying out demining work.
"It is possible (they could have crossed by mistake) but we cannot believe that just because they said that," Khalid said.