Sudanese warplanes have launched an attack on a major South Sudanese town, bombing the capital of the oil-producing Unity border state, according to South Sudan officials.
Bombs were dropped at dawn on Thursday, targeting a strategic bridge on the Rubkhona airstrip just outside Beintu town close to a UN compound, which lies about 60 kilometres from the frontier as clashes between the recently separated nations continued for a third day.
The air raids came after South Sudanese troops captured the oil-rich border town of Heglig which is internationally recognised as part of Sudan, according a Sudanese government minister.
The military advance by South Sudan and Sudanese air raids brought condemnation from the United Nations Security Council as UN Secretary-General Ban Ki-moon called on both sides to withdraw from the other side's territory and said he was "alarmed by the escalation in fighting".
Al Jazeera'a Nazanine Moshiri who is reporting from Juba says both sides are sticking to their positions.
"All of this will add to the already tense situation in the Unity state," said our correspondent.
Sudan's ambassador to the United Nations, Daffa-Alla Elhag Ali Osman, said he had filed a complaint to the Security Council condemning the "heinous attack" on Heglig.
"We will decide to retaliate, and retaliate severely, deep inside South Sudan if the Security Council doesn't address the situation", Ali Osman told reporters.
A statement on Khartoum's official SUNA news agency warned of "destruction" in South Sudan.
Focal point of fighting
Heglig lies along the disputed border between the two African nations and has been the focal point of nearly two weeks of clashes between their armies, which have prompted the collapse of African Union-mediated talks.
The region is home to oil fields that account for about half of Sudan's oil production, a critical source of income for the country's flagging economy.
The two rivals fought a civil war that lasted decades, and never reached a deal to share the region's oil resources or delineate their exact border during negotiations which led to South Sudan's cessation last year.
A 2009 ruling by the Permanent Court of Arbitration in the Hague placed Heglig in Sudan's Southern Kordofan region. But South Sudan has disputed the ruling, asserting that the region is in South Sudan's Unity State.
South Sudan's army said it moved into Heglig on Tuesday after repelling an attack launched by Sudanese Armed Forces against a position near the border town of Teshwin.
Sudan President Omar al-Bashir was scheduled to visit South Sudan for a summit April 3, but the talks were scrapped in the wake of the clashes.
President Barack Obama earlier this month called South Sudan President Salva Kiir to ensure that South Sudan's military exercised maximum restraint and was not involved in or supporting fighting along the border.
In a statement, the African Union called upon both countries to resolve all outstanding issues "in a peaceful way in accordance with the overriding principle of establishing two viable states in Sudan and South Sudan".