The only Darfur rebel faction to sign a May 2006 peace deal with Khartoum says it is under attack from government forces and allied Janjaweed militia.
Khalid Abakar, of the Sudan Liberation Army (SLA) faction led by Minni Minnawi, said the town of Muhajiriya, which they control, was half-burned.
The SLA told the BBC the assault was a continuation of a Sudanese army offensive on Haskanita.
That town was razed to the ground and looted while under government control.
It followed the attack on an African Union base there on 29 September in which 10 AU troops were killed.
The BBC's Amber Henshaw in Khartoum says it appears fighting in Muhajiriya is ongoing.
The SLA rebels told our correspondent that they came under fire from government planes, after which mixed government forces and militias engaged their men.
SLM/A FACTION LEADERS
Minni Minnawi signed 2006 DPA
Abdel Wahid al-Nur now in Paris
Ahmed Abdel-Shafei leads SLM-Classic
Suleiman Jamous, humanitarian coordinator of SLM-Unity
Mr Minnawi took an official post as "senior assistant" to the president of the Republic of the Sudan, but his group's relations with the government have become increasingly strained.
Most rebel groups and the government have committed themselves to take part in new peace talks in Tripoli expected to begin later this month.
There are suggestions that the spate of recent attacks is connected to the repositioning of forces ahead of these talks.
But analysts say that not only are the rebels splintered - conservative estimates say there are at least 12-15 factions - but that there are also splits between tribes, between leaders in the field and political figures in exile
An assortment of rebel factions has already spoken out, blaming the government and Janjaweed militias for the destruction of Haskanita - and some go further, saying the government was behind last week's attack on an African Union base.
The destroyed town was close to the base where 10 AU soldiers died
A statement from the Sudanese armed forces said attempts to implicate them are "unfortunate and illogical".
The government statement - from the office of the armed forces' spokesman - said the army had "fully carried out its role of pursuing those accused of the recent massacre".
"The burning of Haskanita is an issue relating to the area's internal security," the statement added.
The UN observer mission has not commented on which forces destroyed Haskanita.
One Darfuri rebel group, the Justice and Equality Movement told the BBC that there was proof that the government forces were involved, thanks to a photograph of a green military tank in the town.
Claim and counter-claim
The UN said that only the school and mosque were left standing in the town, which had been home to 7,000 people though many fled when the AU base came under attack on 29 September.
The commander of the AU-UN peacekeeping force blamed the attack on a rebel splinter group "who broke away from a faction called SLA United".
Another leading rebel, Suleiman Jamous, who represents the Southern Liberation Movement and is based in Chad, said he too believes the Sudanese army carried out the attack on Haskanita and said up to 100 people were killed.
The UN has dismissed this claim.
For its part, the JEM denies its forces had anything to do with the attack on the AU base and alleges that too could also have been the work of government forces.
"Only government fighters were in the area," Haroun Abdul Hameed said, "the rebels had withdrawn".
By next year the UN and AU are meant to have deployed the world's largest peacekeeping force - 26,000 troops - to Darfur.
The hybrid force will absorb the 7,000 AU troops in the region who have struggled to protect civilians, admitting they are outmanned and outgunned.
At least 200,000 people have died in Darfur during a four-year conflict and more than two million have been forced from their homes.