"On Friday, our troops shot down two SAF (Sudanese Armed Forces) planes. One was an Antonov bomber in Kalkul and the other was a MiG Joint-3, in Kauda," said
Gamar Delman, media advisor to former deputy governor Abdelaziz al-Hilu , a key member of the northern branch of the Sudan People's Liberation Movement (SPLM), the ruling party in the south.
"The air strikes (this week) have caused the displacement of 75,000 civilians. They took place in nine areas of Southern Kordofan and continued up to yesterday," he told AFP.
The northern army strongly denied the claims.
"The allegations that SAF planes crashed in South Kordofan are completely wrong," army spokesman Sawarmi Haled Saad told reporters in Khartoum.
"The army deeply regrets unbalanced accounts by UNMIS (the United Nations peacekeeping mission in Sudan) of heavy bombardments while it remains silent about the attacks on civilians and their displacement," he added.
Heavy clashes between the Sudanese Armed Forces (SAF) and northern members of the former southern rebel army have raged all week across Southern Kordofan, the north's only oil producing state, with intense fighting in and around the state capital Kadugli.
The violence in central Sudan has poisoned the atmosphere of the north-south negotiations that have been taking place in Ethiopia, where the country's two leaders were due to meet on Sunday, to try to resolve their differences.
Malik Agar, head of the northern branch of the SPLM, said the hope was to find a "solution to big problems."
"We are here for talks to resolve serious issues," he told AFP from Addis Ababa.