At least 20 killed as rival rebel groups clash in South Sudan. (AP Photo/Bullen Chol, File)
Clashes between South Sudan's rebel factions in the strategic town of Kajo Keji, near the border with Uganda, have left at least 20 people dead in the past week, an opposition spokesman said on Monday. 

Lam Paul Gabriel, a spokesman for the Sudan People's Liberation Movement-in-Opposition (SPLA-IO), which is loyal to former vice president Riek Machar, said the clashes erupted last Tuesday between SPLA-IO and National Salvation Front (NSF), which is loyal to former army logistics chief Thomas Cirillo. 

The two opposition groups fighting the government of President Salva Kiir were previously stationed side by side in the area of Kajo Keji, but fighting erupted after NSF forces attacked SPLA-IO bases, killing one person and abducting some others, Gabriel said. 

Fighting is still ongoing in several areas as both sides continue to battle for control of more territory, adding that the SPLA-IO have killed more than 20 NSF forces -- a claim not independently verified. "We don't consider NSF as genuine opposition but a threat to us," Gabriel said. 

"I can't rule out the fact that it is pro-government... because if not, why would they continue to attack our positions in Kajo Keji?" Bismarck Duku, a Kajo-Keji resident, told Xinhua by phone from the northern Uganda region of Yumbe district, where he fled over the weekend, said most of the families who previously stayed at a camp for internally displaced persons have crossed to neighboring Uganda. 

Santo Domic Chol, deputy spokesman of the South Sudan army, the Sudan People's Liberation Army (SPLA), said the army has noticed unusual movement of people and fighting in the area, adding that the SPLA would fight back if the rebels attack its defensive positions. 

South Sudan has been embroiled in more than three years of conflict that resulted in one of the fastest growing refugee crisis in the world. 

 A peace deal signed in August 2015 between the rival leaders under United Nations pressure led to the establishment of a transitional unity government in April, but was shattered by renewed fighting in July 2016. The UN estimates that at least 4 million people have been displaced internally and externally.