JUBA (AFP) - The United Nations Children's Fund (Unicef) said on Monday it was "extremely concerned" over the looting by South Sudan government troops of school supplies and backpacks that were supposed to be destined for children.

The complaint came after large numbers of heavily-armed South Sudanese government soldiers, who are battling a seven-week-old rebellion, were photographed kitted out with bright-blue Unicef 'back to school' bags on their shoulders.

"We are of course extremely concerned to see this flagrant abuse of Unicef education materials by combatants," Unicef spokesman Sarah Crowe told AFP.

"A large amount of Unicef supplies - along with humanitarian supplies from other organisations as well as stores from schools and hospitals - have been looted in many locations during the conflict in South Sudan," she added.

"Such thefts display a complete disregard for the principle of protection of civilians and respect for humanitarian work," Ms Crowe said, urging the warring factions to "take appropriate action against the theft and use of supplies that are intended for the welfare of civilians - especially children".

The conflict in South Sudan has seen widespread looting of aid agencies by both government forces and the rebels, including vehicles, food stockpiles and medicines from organisations including the International Committee of the Red Cross (ICRC), Doctors Without Borders (MSF) and the World Food Programme (WFP).