Clashes have erupted between Sudan's army and rebels in the western Darfur region and in a southern state, killing dozens of people, including several civilians, the Sudanese military says.
Civilians were among those killed in the latest violence, which took place on Thursday.
The government of President Omar al-Bashir is battling an alliance of rebel groups operating in Darfur and in two states bordering neighbouring South Sudan.
Speaking late on Friday, Al-Sawarmi Khalid, a Sudanese military spokesman, said that the army had killed 77 rebels in two separate clashes on Thursday in South Kordofan, a state bordering South Sudan, and in North Darfur state. He said that 21 civilians were also killed.
The army is fighting rebels in the Sudan People's Liberation Movement (SPLM-North) in South Kordofan and Blue Nile states.
Khalid said SPLM-North rebels attacked the village of Hajr al-Dum in South Kordofan. He said 45 rebels and 21 civilians were killed in the violence, among them women and children.
"The armed forces are continuing to expel the rebels from the area," he said.
The SPLM-North, however, gave a different account of the violence.
Arnu Lodi, a rebel spokesperson, said that SPLM-North forces had attacked an army position near Hajr al-Dum and driven out all troops from the area.
One soldier was killed and five wounded, Lodi said in a statement.
Military spokesperson Khalid said that the army had also repulsed a rebel attack on the village of al-Adradib in North Darfur, killing 32 anti-state fighters.
Several soldiers were killed or wounded, he told Sudanese state television, without giving any figures. He said that the army had also seized equipment belonging to the rebels.
The Justice and Equality Movement (JEM), one of the biggest rebel groups in Darfur, however, said that dozens of soldiers had been killed and that an army attack on the village had been beaten back.
"The air forces bombed the area and killed tens of civilians," Jibril Adam, a JEM spokesperson, said.
He also said the army attacked the area of Tanga in South Darfur. "Our forces dealt a major blow to the Sudanese Armed Forces and their militias in Tanga," Adam said.
The JEM said it had seized vehicles from government forces.
Events in Darfur and South Kordofan are difficult to verify due to a lack of access for journalists to the remote areas.
The SPLM-North, JEM and two other Darfur rebels groups formed an alliance last year with the aim of toppling President Bashir.
Al Jazeera's Harriet Martin, reporting from Khartoum, said that the alliance between the rebel groups had exposed how much pressure the Sudanese military was under.
Sudan and South Sudan, meanwhile, are currently holding talks in Ethiopia to discuss a border security agreement.
Martin reported that the clashes were likely to have a direct impact on those talks.
"What these clashes do, they shed light on why, within just a couple of days, those peace talks under the AU in Addis Ababa have fallen into great difficulty. And that's because the first item on the agenda was to the demilitarised zone," she said.
"This would have demanded that both the Sudanese and South Sudanese army pull back their troops from the border 10km. But clearly in the light of these clashes, from the point of view of the Sudanese military, their priority is quite different. From their point of view they want to secure the control of their territory, which now faces insurgency in several places rather than start conforming at this moment to the agenda of an international peace talks."