KHARTOUM (Reuters) - Sudan's army fought rebels in the oil-producing state of South Kordofan last week, both sides said on Saturday.
The rebels said they had killed nine government troops, but the army denied this.
Fighting has taken place since last June in South Kordofan between the Sudanese army and rebels from the northern wing of the Sudan People's Liberation Movement, who want to topple the Khartoum government.
Clashes spread to neighbouring Blue Nile state, which also borders newly independent South Sudan, in September.
The violence has already forced about 417,000 people to flee their homes, more than 80,000 of them to South Sudan, the United Nations estimates.
Both Blue Nile and South Kordofan contain large groups who sided with the south in a decades-long civil war, and who say they continue to face persecution inside Sudan since South Sudan seceded in July.
The SPLM is now the ruling party in the independent south and denies supporting SPLM-North rebels across the border.
The SPLM-North rebels said they had killed nine soldiers, destroyed three tanks and seized military equipment in clashes at Tees near the southern border on Monday. They also seized three army vehicles in another attack in the same area on Tuesday, they said in a statement.
Army spokesman Sawarmi Khalid Saad confirmed military operations had taken place in the town of Tees to reopen a road but denied any soldiers had been killed.
"These areas are under army control," he said.
Events in South Kordofan and Blue Nile are difficult to verify because aid groups and foreign journalists are banned from areas where fighting takes place.
SPLM-North is one of a number of rebel movements in underdeveloped border areas who say they are fighting to overthrow Sudan's President Omar Hassan al-Bashir and end what they see as the dominance of the Khartoum political elite.
Sudan and South Sudan, who still have to resolve a range of issues including the sharing of oil revenues, regularly trade accusations of supporting insurgencies on each other's territory.
Their armed forces clashed at Jau in a region claimed by both sides last month in a rare direct confrontation.
Locals have faced air raids and sporadic ground fighting, according to rights groups and refugees, although Sudan denies it is bombing civilian areas.
(Reporting by Khalid Abdelaziz; Writing by Ulf Laessing; Editing by Ben Harding and Peter Graff)