The UN expressed alarm Wednesday at Sudan's intensified bombing of a troubled border state and US President Barack Obama urged an immediate ceasefire as clerics and activists alleged ethnic cleansing.
Obama said there was no military solution to the conflict in South Kordofan, and urged the leaders of north and south Sudan to live up to their responsibilities.
"The government of Sudan must prevent a further escalation of this crisis by ceasing its military actions immediately, including aerial bombardments, forced displacements and campaigns of intimidation," Obama said in an message recorded late on Tuesday for a US broadcasting network.
After a wave of air strikes on Tuesday, allegedly targeting rebel positions in the Nuba Mountains, the United Nations peacekeeping mission in Sudan (UNMIS) said the situation in South Kordofan remained "extremely volatile and tense."
Earlier, a UN report said the Sudan Red Crecent Society had collected 25 dead bodies in the state capital Kadugli, which has witnessed some of the fiercest fighting, and cited local sources indicating that 64 people had been killed in aerial bombardments since the clashes first erupted.
"There is a growing sense of panic among some of the displaced populations who find themselves trapped by the ongoing violence and the ethnic fault lines," the UN humanitarian office reported.
Heavy fighting between the northern Sudanese Armed Forces and allied militiamen against fighters aligned to southern former rebel group the Sudan People's Liberation Army has raged across the state since June 5.
The international Catholic charity Caritas said more than 60,000 people had fled their homes.
Caritas said that more than 70 percent of the population of Kadugli had fled the city, with over 27,000 people fleeing to Kauda and that "an unknown number of people" were believed to be hiding in the Nuba Mountains.
On Tuesday, the SAF appeared to step up its air strikes on former rebel strongholds, where the indigenous Nuba peoples fought with the SPLA during the devastating 1983-2005 civil war between north and south.
UNMIS said jet fighters dropped 11 bombs around the town of Kauda on Tuesday morning, as part of its ongoing bombing campaign that was causing "huge suffering" to the civilian population.
The SAF denied it was targeting civilians, saying it was battling a rebellion in South Kordofan, while a ruling party official at the information ministry insisted the Sudanese government treated all ethnic groups equally.
"Saying that the army is targeting the Nuba is false information (from the rebels), to show the world that they are suffering from marginalisation," Rabie Abdel Ati told AFP.
"This is due to the failure of Abdelaziz al-Hilu in the elections (for state governor last month)," he added.
A Sudanese human rights group reported this week that Antonov bombers had killed more than 65 people in air strikes in South Kordofan since the start of fighting.
The Sudan Democracy First Group, in a six-page report, accused the SAF of pursuing a genocidal campaign against the Nuba in South Kordofan, supported by a feared civil war militia that now forms part of the northern army.
The accusations were echoed by opposition MPs in Khartoum.
"(The government) want to pursue their Arab-Islamic state and anyone who opposes that will be eliminated. And the Nuba have the loudest voice in that, saying they are proud to be Nuba," Ahmed Saeed, a Nuba activist and MP for South Kordofan, told AFP.
Daniel Deng Bul, who as the Episcopal Archbishop of Sudan is the country's senior Anglican clergyman, also accused Khartoum of pursuing a policy of "ethnic cleansing" in South Kordofan, in a statement on Tuesday.
The UN refugee agency, meanwhile, has appealed to the Sudanese authorities to provide air and road access for humanitarian agencies to South Kordofan, where UN offices and warehouses have been looted.
Planes have been refused permission to land and roadblocks were hampering access by land, spokeswoman Melissa Fleming said.
Reports are also emerging of alleged extra-judicial killings carried out by the armed forces on Sudanese UN staff and on civilians, during house-to-house searches for suspected SPLA sympathisers.
The United States has threatened to halt the normalisation of its ties with Sudan, warning the government it faced deeper international isolation if it did not halt the violence, which threatens to cast a pall over the run-up to southern independence next month.© ANP/AFP