By Parach Mach

JUBA, South Sudan

Fighters loyal to former Vice President Riek Machar claimed taking control of a strategic northern military base near the Sudanese border on Tuesday -- a development that was swiftly rejected by the government as “wishful propaganda”.

The base is reportedly used by the army to launch assaults on rebel strongholds in the Upper Nile region.

Paul Lam, deputy spokesman for Machar’s forces, told Anadolu Agency their fighters had taken control of Kuek town in the Upper Nile following clashes with government forces on Sunday and Monday.

Lam added the fighters had seized military equipment, ammunition and inflicted heavy losses on government troops. He portrayed the so-called victory as a major blow to President Salva Kiir's recently declared unilateral cease-fire and national dialogue in the region.

A military spokesman confirmed heavy fighting in Upper Nile, but dismissed the rebel claims of victory on the frontlines.

“Yes, there has been fighting in Upper Nile; Riek Machar rebels keep attacking our positions but they have never come close to our bases; this is a wishful and propaganda,” Brig. Santos Dominic Chol told Anadolu Agency via telephone.

They raided our positions in Kuek but neither killed any of our troops nor captured an inch of this town, Chol said.

Claims that opposition forces have retaken Kuek came as heads of state and governments from the African trade bloc -- the Intergovernmental Authority on Development (IGAD) -- convened a summit on Monday to discuss the dire security and humanitarian situation in South Sudan.

The IGAD assembly had urged warring parties in South Sudan to reciprocate the call for a cease-fire as well as renounce violence. The assembly welcomed the declaration of cease-fire by President Salva Kiir and called upon him to strictly implement it.

Last month, the UN mission in South Sudan said the conflict was escalating in the war-ravaged country despite peace efforts.

The conflict in South Sudan, the world’s youngest nation, began in December 2013 and has led to a humanitarian crisis. Some 7.5 million people, two-thirds of the population, require humanitarian assistance.

Around 1.6 million people have fled the country as refugees, while a further 1.9 million are displaced internally.