Sudan is sending hundreds of troop reinforcements to the troubled Blue Nile region, state-linked media said on Thursday, after reports of fighting in a strategic border town.
Battalion 191 has arrived in the Blue Nile state capital Ed Damazin and two more battalions are expected, reported the Sudanese Media Centre which is close to the security apparatus.
It said the move aims to "improve the security in Blue Nile... to clean the state of rebels."
Witnesses also reported fighter planes and helicopters active in the area.
Sources told AFP earlier this week that there has been fighting in El Kurmuk, about 240 kilometres (150 miles) south of Damazin.
Rebels of the Sudan People's Liberation Movement-North (SPLM-N) claimed last Sunday to have pushed into Kurmuk's southwest but since then have made virtually no comment except to claim fighting continues in the town.
Sudan's army spokesman Sawarmi Khaled Saad could not be reached on Thursday.
Last Sunday, he denied the rebels were near Kurmuk and said their claim was a "fabrication" designed to damage army morale.
Kurmuk, an important trading centre on the Ethiopian border, is the third-largest town in Blue Nile and has been in government hands since November 2011.
Sudan's government severely restricts access to Blue Nile and South Kordofan, two states where the SPLM-N has been fighting since 2011. Khartoum accuses South Sudan of backing the SPLM-N but the South denies involvement.