The number of people displaced from Sudan's disputed Abyei region after its seizure by northern troops has reached 150,000, a southern minister says.
"The situation is terrible - they are running in fear from brutal violence, without shelter," Humanitarian Affairs Minister James Kok Ruea said.
The BBC's Peter Martell in Juba says the figure is a huge leap from UN estimates of between 30,000 and 40,000.
Meanwhile, the north says it can start talks on the crisis this weekend.
The northern negotiator on Abyei, Al-Dirdiri Mohammed Ahmed, told the AFP news agency he hopes the negotiations will take place in Ethiopia on Saturday hosted by the African Union mediators.
Analysts fear the dispute over the region, also claimed by South Sudan which is due to become independent in July, could reignite the north-south war in which some 1.5 million people died.
On Thursday, southern President Salva Kiir said he would not lead his people back into conflict with the north over Abyei and said talks would be the best way to resolve the dispute.
Mr Kok Ruea said people had fled from Abyei, which is believed to have an estimated population of 110,000, and border regions since northern troops took over Abyei town at the weekend.
Our correspondent says the UN's lower figure is based on people counted through aerial surveillance.
Detection is difficult because many of those fleeing are believed to travelling off the main roads, hiding in surrounding bush for fear of aerial attack by northern aircraft, he says.
A UN assessment report released on Friday said its air and ground patrols indicated the area was empty except for a "heavy presence of armed men".
"The air assessment mission flew over 10 villages north and south of Abyei town," the report said.
"No displaced populations were observed… burnt tukuls [thatch huts] in several villages were reported."
Most of those fleeing Abyei were from the Dinka Ngok, a southern ethnic group who are the permanent residents of the region.
After this week's UN Security Council trip to Sudan, US ambassador to the UN Susan Rice said the occupation of Abyei was a violation of the 2005 peace deal which ended the 22-year civil war.
"There's real concern that the government of Sudan may have taken a decision to continue to occupy Abyei for its own political advantage for an indefinite period," the AP news agency quotes her as saying.
The UN has said it believes militiamen from the Misseriya ethnic group were responsible for shooting at one of its helicopters on Wednesday.
The Misseriya are northern nomads and one of two groups, along with the Dinka Ngok, to claim Abyei. The Misseriya were armed by Khartoum and used to attack the south during the civil war.
Under the 2005 peace agreement, Abyei was granted special status and a joint administration was set up in 2008 to run the area until a referendum decided its fate.
That vote was due to take place in January but has now been postponed indefinitely.