Sudanese troops on Thursday occupied a key stronghold of the southern-aligned rebels they are battling in South Kordofan state, the information minister said.
The claims were denied by the rebels, however, who said heavy fighting was ongoing.
“The armed forces managed today to retake the area of Taruje, south of the town of Kadugli, from the rebels,” Kamal Obeid was quoted as saying by the official SUNA news agency, describing it as an “important victory” for the Sudanese army.
But a rebel fighter in the embattled border state insisted the claim was not true, saying that since Wednesday there had been heavy fighting in an area 15 kilometers (nine miles) east of Taruje, which itself remained under the control of the SPLA/M-North rebels.
“They are attacking with heavy artillery -- they have been shelling the area since yesterday -- and they have five tanks. But they will be forced back to Talodi, where they came from,” Mubarak Abdul Rahman told AFP by phone.
“We didn’t get the number of casualties from the fighting because the operation is still going on,” he added.
Fighting erupted in South Kordofan in June between the army and militiamen who fought alongside the ex-southern rebels during their 22-year conflict with the north, as Khartoum moved to assert its authority within its borders ahead of southern independence in July.
A similar conflict broke out three months later in nearby Blue Nile state.
It has been very difficult to verify information about the ongoing violence, since the Khartoum government has prohibited foreign aid workers and journalists from visiting the region.
But the clashes along the poorly defined north-south border have badly affected relations between the former civil war enemies, with each side accusing the other of supporting rebels within their territories.
In recent weeks, there has been evidence of cross-border attacks.
The SAF said on Wednesday that a group of SPLA soldiers, the rebels turned regular army of South Sudan, had advanced nine kilometers (six miles) into Sudan's White Nile state with the aim of looting civilian property.
It claimed in a statement to have repulsed the group, killing an unspecified number of them and capturing one SPLA soldier.
A South Sudanese official, Renk county commissioner Deng Akuei, confirmed that “some of the SPLA soldiers” were killed in clashes between the two sides.
But he said the Sudanese army had attacked an SPLA patrol south of the border, in Upper Nile state.
“The Sudan Armed Forces ambushed the SPLA patrol in the Bakhit Hameda area and some of the SPLA soldiers were killed and some were injured,” he added.
Last month, the Sudanese Armed Forces (SAF) bombed a refugee camp in South Sudan's Unity state, according to eyewitnesses, causing international outcry.
The United Nations refugee agency said last week that the number of people fleeing the unrest in Sudan's two war-torn border states is likely to reach 100,000 by the end of the year, up from around 80,000 now.