Rebels in eastern Sudan have been attacked by government forces in their main stronghold, they say.
Eastern Front rebels said at least two children had been killed in the aircraft and artillery attacks.
Neither Sudanese officials nor independent sources have confirmed the fighting near the town of Hamesh Koreb.
Peace talks are due to start in Libya next week between the government and rebels, who complain of discrimination by central government.
The rebels later said that the government forces had withdrawn from the town.
Two international aid agencies have withdrawn from the region, citing fears of instability.
Sudan says the rebels are backed by Eritrea, whose border is 50km from Hamesh Koreb.
The BBC's Ed Harris in Eritrea says the town is a scruffy mixture of mud huts, set in dirt tracks, palm trees and dry river-beds.
'Dangerous'
Former rebels from the southern SPLA have been ordered to leave the town by the soldiers, reports the AFP news agency.
The SPLA signed a power-sharing deal with the government a year ago and a spokesman for the group said the eviction order by was an "act of aggression" by heavily armed men backed up by four tanks.
"It is a violation of the peace agreement and it is very dangerous," Major General Elias Waya Nyipuocs told AFP.
The SPLA troops were due to leave the town this week and the International Crisis Group think-tank has warned that their withdrawal could lead to a dangerous power vacuum.
Eastern Front rebels complain that the region's Beja and Rashaida communities have been marginalised in favour of Arab groups and want a fair share of resources.
The area is home to Sudan's main port, Port Sudan.
Attempting to defuse he rebellion, Khartoum said last year it would give about $88m to develop east Sudan.