South Sudan's soldiers have killed 14 people in volatile Jonglei, an eastern state that has suffered ethnic massacres, alleged disarmament-related abuses and rebellion, officials said Monday.

Local officials insist the victims were civilians, but the army claims they were gunmen following rebel leader David Yau Yau, a former theology scholar from the Murle people who have been fighting on and off since April 2010,

The killings took place last week near the remote village of Gumuruk in Jonglei's Pibor county.

"The army took civilians in Gumuruk and killed 14" Murle people, Pibor commissioner Joshua Konyi told AFP on Monday, claiming the victims were executed.

"They collected 15 of them, and when one person ran away, they killed seven there on the spot and took seven people to near Gumuruk and killed them," he added, basing his information on reports from the settlement.

However, Jonglei governor Kuol Manyang said the official military reports he had said the army "fought with the Yau Yau rebels in Gumuruk, 14 people were killed and guns captured."

The army was not immediately available for comment.

South Sudan, the world's youngest nation after winning independence in July 2011 after decades of war, is struggling to maintain a fragile peace in the face of militia forces and an often unruly rebel-turned-regular army.

More than 2,600 people have been killed in Jonglei in the past 18 months, according to the United Nations.

Peter Gazulu, Pibors former human rights commissioner, insisted that those killed last week were not with the rebels.

"Among the dead I have my brother-in-law, and he never joined Yau Yau. . . All these people were not in Yau Yaus group," Gazulu said, adding that at least one of those killed had been an elderly man.

After losing out on a seat in April 2010 elections, Yau Yau rebelled against Juba's government, but accepted an amnesty in June 2011. He later returned to rebellion in April.

Liam McDowall, spokesman for the UN peacekeeping mission, said they were "aware of the reports and we are actively looking into the matter."

Both Human Rights Watch and Amnesty International have condemned a string of reported abuses -- including shootings, torture and rape -- as security forces crack down on those seen to support the rebels.

Over 600 people were massacred in Jonglei's Pibor area after an 8,000-strong militia force went on the rampage last December, according to UN, although local officials reported the figure to have been even higher.

Jonglei was one of the areas hardest hit in Sudan's 1983-2005 north-south civil war, which ended in a peace deal that paved the way for the South's full independence.

But the new nation is awash with guns, while heavily armed communities that were once pitted against each other during Khartoum's rule remain rivals.