Ten aid workers kidnapped in South Sudan by opposition forces last week have been returned to the capital, Juba.

Ten aid workers abducted in South Sudan last week have been released.

The workers – kidnapped while travelling in a convoy near the southern city of Yei on April 25 – were transported from the area by an International Committee of the Red Cross (ICRC) aircraft to the capital, Juba, on Monday, the group said in a statement.

The three UN staff and seven aid workers from several different organisations are all South Sudanese nationals.

Fighters from the Sudan People’s Liberation Movement-in-Opposition (SPLM-IO) were responsible for seizing the convoy, alleging the workers had entered an area “without any clearance”.

Civil war

Aid workers have frequently been targeted by armed forces operating in South Sudan since an ethnically charged civil war erupted in December 2013, when troops loyal to President Salva Kiir and then-Vice President Riek Machar clashed.

The conflict has resulted in the deaths of tens of thousands of people – including at least 98 aid workers – and led to more than four million people being displaced from their homes, according to the UN.

Francois Stamm, head of the ICRC in South Sudan, called on Monday for all those involved in the conflict to refrain from attacking aid workers.

“While we are relieved these 10 humanitarians have been released, we want to remind all parties to the conflict that aid workers are never a target,” Stamm said.

The United Nations said it was “outraged” by the deteriorating security situation facing humanitarians.

“I am deeply concerned by the insecurity faced by aid workers in South Sudan, who are risking their lives to save others,” said Alain Noudehou, the UN’s humanitarian coordinator for South Sudan.

‘Misunderstandings’

Opposition forces loyal to Machar said the UN is sending humanitarians into rebel-controlled areas without clearance.

“This is undermining the leadership of the [opposition], and it has to stop immediately as it has resulted into misunderstandings and endangering of lives of the workers and our displaced population,” opposition spokesman Lam Paul Gabriel said in a statement.

The opposition’s leadership found out about the kidnapped aid workers two days ago and immediately ordered their release, Gabriel told The Associated Press.

But the UN has said it never enters an area to deliver aid until negotiations with all parties are completed.

Aid workers operating in South Sudan were held by armed groups twice in April, and three times during the last six months, according to the UN.