JUBA (Reuters) - Ten aid workers have gone missing in the South Sudanese town of Yei, a U.N. official said on Thursday, the latest incident involving relief staff in the war-ridden country.

Alain Noudehou, the United Nations Humanitarian Coordinator for South Sudan, said a convoy of U.N. and other aid workers had been heading to Tore from Yei, in the Central Equatoria region, early on Wednesday.

The whereabouts of the 10, all South Sudanese, were now unknown. “We are deeply concerned about the whereabouts of these humanitarian workers and are urgently seeking information about their well-being,” Noudehou said.

Aid workers are often targeted by armed groups operating in South Sudan, which has been in the grip of war between supporters of President Salva Kiir and those of his former deputy Riek Machar since 2013.

Tens of thousands of people, including nearly 100 relief workers, have been killed.

Noudehou said of the missing people, one was working for the humanitarian office UNOCHA, two for UNICEF, one for the South Sudanese Development Organisation, two for aid group ACROSS, three for Plan International and one for Action Africa Help.

Earlier this week, the International Committee of the Red Cross said it had suspended operations in Leer after their field base was shot at on April 10. It evacuated its staff to the South Sudanese capital Juba.

In mid April, rebels said they had freed seven aid workers detained for nearly three weeks in Central Equatoria on accusations of spying for the government.

An aid worker was also killed when gunmen shot at his agency vehicle near the northern town of Bentiu.

Both rebels and government forces stand accused of targeting humanitarian workers and sometimes blocking access to relief and hijacking food and other aid.

Lam Paul Gabriel, rebel SPLA-IO deputy spokesman, said he had received reports of aid workers’ disappearance and his forces were investigating with their commander in the ground.

“I am not denying or accepting that we are the ones responsible for this but we are investigating because that is our territory, but we should not ruled out the presence of other armed forces,” he said.

He said there were also a separate armed group called NASA, as well as government troops present in the area.

“So until we get that report from the ground commander, we will not be able to confirm,” he said.