Thousands of Sudanese need food, water and shelter, a source in an aid organisation said on Tuesday, after they fled a widening rebel offensive that swept through a previously peaceful area.
The source in Sudan's Humanitarian Aid Commission (HAC) told AFP that several thousand from one district alone, Abu Kershola, had converged on the North Kordofan town of El Rahad.
"They are in a miserable situation," said the source, asking for anonymity.
He said a team from HAC is in the area to assess people's needs.
An AFP photographer reported that government vehicles were still ferrying people on Monday night to three camps for displaced people in the El Rahad area. Some of the homeless had sought shelter in schools.
Abu Kershola, in the far north of South Kordofan state, was one of several areas in North and South Kordofan which the Sudan Revolutionary Front (SRF) rebel alliance said it attacked on Saturday.
Insurgents on Tuesday claimed to still be in control of Abu Kershola, where they said they seized an army garrison.
Villagers from that area earlier told AFP they were living rough under trees after fleeing.
The rebels briefly occupied Umm Rawaba, the second-largest town in North Kordofan. Residents complained their community had been left undefended as the insurgents shot up government buildings, hitting policemen.
Government bombers and helicopters were in the air after the attack, they said.
AFP's photographer saw that the town's power station had been left blackened and burned.
The glass facade behind the colonnades of an official-looking three storey building had been shattered, while smaller buildings had been damaged by fire.
Except for occasional rebel forays over the border from the conflict-plagued Darfur region, North Kordofan had been generally peaceful.
SRF said they attacked as part of their strategy to reach the capital Khartoum and overthrow the 24-year regime of President Omar al-Bashir.