Rebels in Sudan's oil-producing border state of South Kordofan said on Tuesday, April 16 they had seized a military base near the state capital, underlining tensions in the region that could undermine the recent detente between Sudan and South Sudan, Reuters reported.

Sudan and South Sudan split apart in July 2011 under a peace deal that ended decades of civil war. The rebels in South Kordofan and Blue Nilehad sided with the South's fighters during the war but were left in Sudan in the partition.

Khartoum has accused the South of backing the rebels. Juba denies this, but analysts and diplomats say the allegation is credible. The dispute has strained ties between the nations, which came close to all-out war in border clashes last year.

The neighbors agreed in March to resume pumping oil through pipelines from south to north and to a timeline to withdraw troops from their 2,000 km (1,200 mile) border, after months of African Union-brokered negotiations in Addis Ababa.

Khartoum has since said it is ready to talk directly to the rebels in South Kordofan and Blue Nile, known as the SPLM-N, and Sudanese President Omar Hassan al-Bashir went to Juba last week, his first visit since southern independence.

But on Tuesday, SPLM-N spokesman Arnu Lodi said the insurgents had taken control of a military garrison at Ghandur, about 18 km east of the state capital Kadugli.

"Our forces captured the Ghandur area after heavy fighting yesterday," he told Reuters. He said the rebels had killed 13 government soldiers and captured weapons and ammunition.

On Sunday, Lodi said the rebels had called on residents to evacuate Kadugli, which had become a "military target".

Sudan's foreign ministry described the SPLM-N's targeting of the city as "criminal" and said the rebels were undermining peace and stability in the area.

Fighting between the rebels and government forces in South Kordofan and Blue Nile has forced hundreds of thousands of people to flee their homes.