The Sudanese army has been clashing with opposition fighters in the Blue Nile state for at least two months [Reuters]

Sudanese armed forces have seized the rebel stronghold of Kurmuk in Blue Nile state, both sides said, after two months of heavy fighting on the border with newly independent South Sudan.

"Our troops entered the town of Kurmuk, expelled the insurgents and killed and wounded many [them] and they are
now cleansing the town," Sudan's defence ministry website said on Thursday.

Violence in Sudanese border states has soured talks between Khartoum and former civil war foe South Sudan. The two states have yet to resolve how to share oil revenues or other assets after South Sudan seceded as part of a 2005 peace deal. 

"The SPLM troops have withdrawn from Kurmuk for strategic reasons. The Sudanese army controls Kurmuk but this is not the end of the war in Blue Nile," said Sulaiman Othman, a spokesman for SPLM-North in Blue Nile.

Blue Nile and South Kordofan are north of the new border and remain part of Sudan, but are home to many who sided with the south during one of Africa's longest and deadliest civil wars. 

Both sides have also failed to find a solution for the disputed border region of Abyei which Khartoum seized in May. 

Border violence

Fighters in border states say they have been politically and economically marginalised by Sudan's government. Khartoum accuses them of trying to spread chaos and says it will not tolerate armed militias on its side of the border. 

Fighting between the Sudanese army and SPLM-North fighters erupted in Blue Nile in September, spreading from neighbouring northern state of South Kordofan where violence began in June. 

Khartoum accuses South Sudan of backing the fighters in both states. Juba has denied the charges. 

Border violence has also badly affected ties between Sudan and Western powers. Washington extended trade sanctions this week that have been in place since 1997.