Dozens dying each day along Sudan's border: rebel - Reuters

Khartoum dismissed the accusation on Wednesday, saying it had the humanitarian situation under control and accusing the rebels of using civilians as pawns in their armed insurgency.

Hundreds of thousands of people have fled their homes in Sudan's Blue Nile and South Kordofan border states since fighting between rebels and government forces broke out last year, according to the United Nations and aid groups.

The United States has warned of an impending famine in the region and called on Khartoum to ease restrictions on foreign aid agencies.

Malik Agar, the former governor of Blue Nile who now heads the rebel umbrella Sudan Revolutionary Front (SRF), told Reuters Khartoum's restrictions had created a humanitarian crisis.

"As we speak the situation is catastrophic. People are not attended to. All along this time they have been suffering from lack of food and medicine," he said in an interview late on Tuesday.

"Approximately, we are having 30 to 40 deaths dying daily in both regions ... There is an element of ... using food as a weapon," he added.

Civilian casualties from Sudan's air strikes were mounting in the two regions, Agar said. Sudan denies targeting civilians.

The conflict in the two states is rooted in decades of north-south civil war in Sudan. The civil war ended with a 2005 peace deal that paved the way for South Sudan to declare independence last year.

But the partition of the country left tens of thousands of fighters, who had battled against Khartoum, on the north side of the border. Clashes resumed in South Kordofan in June and spread to Blue Nile in September, with both sides blaming the other for provoking them.

Rabie Abdelati, an official in Sudan's information ministry, accused the rebels of misrepresenting the humanitarian situation and said Khartoum was working to make sure aid was provided.

"They are trying to create an issue from this to get some political benefit," he said. "I don't think that our government is lagging behind."

REBEL ALLIANCE

Experts say the border areas, mostly rugged stretches of mountainous terrain, often face severe food shortages from June to September.

Khartoum sacked Agar as Blue Nile governor shortly after clashes erupted, and appointed a military ruler.

Agar quickly took to the bush, and joined the SRF when it was formed last year between the Sudan People's Liberation Movement-North (SPLM-N), who operate in South Kordofan and Blue Nile, and other rebels in Sudan's western Darfur region.

Leaders of the rebel group are in Addis Ababa for talks with officials from the United Nations, African Union and the Arab League, who proposed a plan earlier this year to secure aid delivery to rebel-controlled areas.

The discussions are taking place on the sidelines of peace talks between Sudan and South Sudan, which resumed last week.

The two countries are at loggerheads over issues including where to draw the border, how much the landlocked South should pay to transport oil through Sudan, the status of citizens in one another's territory and national debt.

A major point of contention has been Khartoum's accusation that Juba is supporting the SPLM-N rebels - and Juba's charges that Khartoum is supporting insurgents south of the border. Both sides deny the other's claims.

The rebel group says it is fighting to overthrow Sudanese President Omar Hassan al-Bashir and end what they see as the marginalization of minority groups.

(Additional reporting by Alexander Dziadosz; Editing by Andrew Heavens)