Sudan carried out a deadly air strike on a refugee camp in neighbouring South Sudan on Thursday, hours after the south's president accused Khartoum of seeking a pretext for war, officials said.

"Twelve people were killed and more than 20 wounded," said Miabek Lang, commissioner of Pariang County in Unity state where the attack took place.

"Around 2:45 pm (1145 GMT), the Sudan Armed Forces (SAF) targeted Yida town, where the Nuba refugees [from South Kordofan] are and IDPs (internally displaced persons) from Jau [on the border], as well as civilians," Lang said.

The southern army's spokesman Philip Aguer said Upper Nile state, which like Unity state has seen thousands of civilians flee across its poorly defined border with South Kordofan, had been targeted by SAF air strikes.

"Two places have been bombed today. One is Yida, a place for refugees from South Kordofan... The other place is called Marenji... in Upper Nile," near the site of another deadly bombing raid on Tuesday, he told AFP.

There was no immediate confirmation of the casualty toll from UN or other sources and SAF spokesman Sawarmi Khaled Saad categorically denied the military had carried out any air strikes across its southern border.

"This information is completely false. We didn't bomb any camps or any areas inside the borders of South Sudan," Saad told AFP.

"What is going on in South Sudan belongs to the southerners. We don't have any links to this."

UN humanitarian coordinator for South Sudan, Lise Grande, confirmed reports of the cross border attack.

"We are extremely concerned about the more than 20,000 refugees who have sought safety in Yida, fleeing the fighting in South Kordofan," Grande said.

Unity state's governor Taban Deng said: "The refugees and civilians have been bombed in Yida. They dropped about five to six bombs and it is an Antonov bomber."

All of Sudan's oil is produced in the three states hit by violence on Thursday, but about 75 percent of it lies in the south, which has caused major economic problems for Khartoum since southern independence in July.

Just hours before the reported raids, South Sudan's President Salva Kiir accused his northern counterpart Omar al-Bashir of trying to drag the new country back to war and seize its fields.

"This a the proxy war and Bashir would want them to capture the oil fields", Kiir said in a speech, while condemning Tuesday's air strike in Upper Nile that killed seven civilians.

Separately, the Sudanese army on Thursday repulsed an attack by rebels on the South Kordofan town of Talodi, killing "dozens" of rebel troops and capturing a tank, official Sudanese media reported.

Fighting erupted in Sudan's only oil-producing state, between the army and southern-aligned rebels the SPLM-North, just weeks before the independence of the south.

"The attack started at 6:00 am (0300 GMT)... We killed dozens of rebel troops and we are continuing to count the number of casualties. We also captured one tank and destroyed another," Jalal al-Din, the army commander of in Talodi was quoted as saying by SUNA news agency.

Some civilians were injured, including two women and a child, he added.

A rebel spokesman was not immediately available to comment on the claims.

SAF general Bashir Bahi was quoted separately in the SUNA report as saying the army had repulsed the attack and would soon clear the area of rebels.

"We taught them a lesson last week, when hundreds of their men were killed. But it seems they did not understand the lesson," he said.

The UN Security Council was to meet later on Thursday to discuss Sudan, which lodged a complaint against South Sudan last week, accusing it of funding the SPLM-North rebels in Blue Nile and South Kordofan who fought alongside the south's ruling SPLM during its 1983-2005 war with Khartoum.

Kiir earlier denied the accusations, telling reporters they were "a prelude from Khartoum to justify their pending actions against South Sudan."

The southern leader said Khartoum's accusations were "utterly baseless and they are just maliciously planned" by Bashir to deflect from internal problems and mask his wish to reclaim the South.

"Tomorrow, when Bashir invades South Sudan, then he will say yes, he took the action to revenge what was being done to him... They want to engage South Sudan in wars, meaningless wars," he said.

Washington on Wednesday condemned what it called "provocative" bombing by the Sudanese armed forces near the border with South Sudan, and demanded a halt to such strikes.