Sudanese rebels on Friday said they shelled the capital of South Kordofan again after a major battle that killed 70 government troops and seven insurgents.
Seventeen members of the Sudan People's Liberation Movement-North (SPLM-N) were also wounded in the clashes northeast of the capital Kadugli, in what the rebel spokesman said was their worst casualty toll since fighting began in the oil-producing state in June 2011.
"It is the biggest loss that happened to us since the war began," the spokesman, Arnu Ngutulu Lodi, said. "In many cases we've lost two, three, four."
Last October, however, the South Kordofan governor said hundreds of rebels had died in an assault on one town.
Analysts say casualty figures from either side in the war should be treated with caution.
Access to the area is restricted and telephone communications sporadic, making verification of claims by either side difficult. Sudan's army spokesman could not be reached for comment.
The ethnic and religious-minority SPLM-N belongs to an alliance of Sudanese rebels seeking to overthrow the Khartoum regime.
They have reported an upsurge in fighting since Sudan and South Sudan in September signed a deal for a demilitarised border buffer zone designed to cut support for the insurgency.
Lodi said government troops supported by tanks, warplanes and helicopter gunships tried to take rebel-held Dldko village about 20 kilometres (12 miles) northeast of Kadugli in an unusual day-long battle against rebels firing down from a mountain.
He said seven government troops were left on the ground and survivors took away the rest of their dead.
As the army fled towards Kadugli, rebels fired 10 mortar rounds targeting military positions in the town, he said.
Witnesses in Kadugli could not be reached for comment.
The rebels have cited a series of aerial bombings as justification for their periodic shelling of Kadugli over the past month.
They say they have targeted military installations and killed a number of troops, but official media say several civilians have been killed by rebel mortar fire.
Four mortar rounds fell near the UN Children's Fund compound in Kadugli during shelling early last week, the UN said.
"On October 25, all UN personnel in Kadugli were instructed to temporarily relocate" to a peacekeeping base and the International Organisation for
Migration office outside the town, the UN's weekly humanitarian bulletin said on Friday.
Sudan and South Sudan fought a border war in March and April, leading to a UN Security Council resolution which ordered a ceasefire and settlement of crucial unresolved issues.
The agreement on the border buffer zone was among a series of deals on oil and security which leaders of the two countries hailed as ending their conflict.
The SPLM-N were allies of southern rebels during Sudan's 22-year civil war, which ended with a 2005 peace deal that led to South Sudan's independence in July last year.
Sudan has accused South Sudan of supporting the SPLM-N, a charge which analysts believe despite denials by the government in Juba.
The war in South Kordofan and Blue Nile, where SPLM-N is also fighting, has affected an estimated 900,000 people, but more than a year of talks has failed to get food aid into rebel zones where serious food shortages are reported, the UN has said.