South Sudan accused Sudan on Friday of attacking its military positions in an oil region, imperiling the chances of a promised ceasefire between the neighbours, but Khartoum denied the charge.
The 1,800 km-long (1,200 mile) border between the two countries had been largely quiet for the past 48 hours, raising hopes that they could begin talks to end a series of clashes over oil exports, border demarcation and citizenship that have pushed them closer towards a full-blown war.
South Sudan's army (SPLA) spokesman Philip Aguer said Khartoum was again on the offensive on Friday: "Today they hit our positions with ground artillery in Teshween, Lalop and Panakuach."
Aguer said Sudanese warplanes had also bombed Lalop in South Sudan's Unity state on Thursday and an SPLA position had been shelled in Teshween.
Sudan's army spokesman denied the charge.
"None of this is true. On the ground there are other enemies, like opposition (groups) to the South Sudanese," Sudanese army spokesman al-Sawarmi Khalid said.
U.S. Secretary of State Hillary Clinton called on Sudan on Friday to stop all cross-border attacks, "particularly its provocative aerial bombardments."
Reports of the attacks came after Sudan said it was ready to accede to international demands for a halt to hostilities, albeit with a significant caveat.
"The ministry points out, in light of the repeated attacks and aggressions that South Sudan's army is carrying out, ... the Sudanese armed forces will find itself forced to use the right to self defense," the foreign ministry said on Thursday.
Limited access to the remote border areas makes it difficult to verify often contradictory statements from both sides.
THREAT OF SANCTIONS
The U.N. Security Council on Wednesday passed a resolution threatening Sudan and South Sudan with sanctions unless they stopped fighting and resumed talks within two weeks, endorsing an African Union deadline of May 8 for negotiations to begin.
Sudan's ruling National Congress Party (NCP) has shrugged off the threat, saying such U.S.-backed resolutions "aim to punish Sudan and reward the aggressor," the state SUNA news agency said on Friday.
Sudanese President Omar Hassan al-Bashir, in power since 1989, had at first ruled out negotiations with his southern "enemy." Sudan later said it was willing to talk about "security issues," as both neighbors accuse each other of backing rebel militias. Both deny the charges.
"This is not someone who wants to negotiate. The security problems with north and south have to be addressed first. How could you go for negotiations when someone's armed forces is still in our territory," Mahdi Ibrahim, a leading official from Sudan's NCP, told reporters in Nairobi.
"Let the issues of security be addressed before we hold negotiations on oil and other issues," Ibrahim added.
The African Union has drawn up a seven-point road map for peace that demands both countries withdraw their troops from contested areas and resume talks.
S. SUDANESE TO BE AIRLIFTED
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.
But it lost three-quarters of the oil after Juba's seceded under a 2005 settlement that ended two decades of civil war between north and south. The pipelines to export the oil run through the north, however, and a dispute about how the oil wealth should be divided has stoked fears of war.
The conflict has brought nearly all oil production to a standstill, damaging both countries' struggling economies.
New York-based Human Rights Watch has accused Sudan's forces of conducting "indiscriminate bombings and abuses" against civilians in South Kordofan, a Sudanese region that borders the South Sudan.
The campaign group has said the violence may amount to crimes against humanity. Sudan dismissed the charges.
The Sudanese army has been fighting the SPLM-N, a rebel group, in South Kordofan and Blue Nile, another Sudanese border region, since last year.
"The government does not attack civilians. The ones who are (attacking) are the SPLM-N and this is their creed. The government is committed to protecting its civilians from these rebel movements that indiscriminately loot and kill," Rabie Abdelatie, an advisor at Sudan's information ministry said.
South Sudan's breakaway left tens of thousands of South Sudanese stranded as foreigners in Sudan.
The International Organization for Migration said on Friday the Sudanese government had agreed to help organize an airlift of about 12,000 South Sudanese who had been stranded in Sudan's White Nile state. They will be brought to Khartoum by bus and then airlifted to Juba, IOM said.