The Sudanese government on Sunday denied claims by rebels of the Sudan Liberation Army (SLA) that the army has launched a massive attack in north Darfur, resulting in heavy casualties.

Sudanese military spokesman Brigadier Mohamed Osman Al Aghbash said there were no military operations in that area recently other than routine security work, in remarks carried early Sunday by the government-linked Sudan Media Center.

Rebels claimed government and militia forces attacked their positions on Saturday around the north Dafur towns of Disa, Birmaza and Tawila, causing heavy casualties.

"They are attacking our positions now as I speak," Salah Bob, a field commander from the SLA faction headed by exiled leader Abdel Wahid Mohammed Nur, told Reuters, speaking from Kejadam in eastern Jebel Marra.

"They are government soldiers, and we are fighting back," he added.

"We have seen 63 bodies, they are both SLA and government (soldiers)" said Ibrahim al-Hillo, a commander from the same SLA faction, speaking from Darfur.

"It is heavy, there are more than 20 civilians killed -- but relatives who are trying to contact their family can't reach them, so it may be more," he added.

"The government (forces) are still in the area, we cannot check that yet."

Fighting was continuing Sunday in the eastern Jebel Marra region of west Darfur following government attacks the previous day backed by four helicopters and two Antonov aircraft, a rebel commander said.

A spokesman for the joint African Union-UN peacekeeping mission in Darfur (UNAMID) said they had no reports of fresh attacks but were investigating the claims.