NAIROBI (Reuters) - A United Nations official said on Wednesday 82 aid workers had been killed in South Sudan’s civil war and the number of its citizens displaced by the fighting now stands at 3.5 million.

A U.N. truck drives past displaced South Sudanese families resting in a camp for internally displaced people in the United Nations Mission in South Sudan (UNMISS) compound in Tomping, Juba, South Sudan, July 11, 2016. Beatrice Mategwa/United Nations Mission in South Sudan (UNMISS)/Handout via REUTERS

Two years after its much celebrated birth as an independent state, South Sudan plunged into conflict in December 2013 as rivalry between President Salva Kiir and his then-vice president, Riek Machar, exploded into violence.

A 2015 peace deal was signed but the terms were never fully respected. Persistent suspicions between Machar and Kiir triggered a fresh bout of fighting in July 2016 and violence has since spread to large areas of the country.

Eugene Owusu, the United Nations resident and humanitarian coordinator in South Sudan, said 82 aid workers had been killed in the violence since December 2013.

An estimated 1.9 million people were internally displaced and another 1.6 million were refugees in neighboring countries.

Much of the violence has been motivated by ethnic differences as government troops, mostly drawn from Kiir’s Dinka community, battle rebel forces made up mainly of Machar’s Nuer community and other smaller groups.

In recent weeks fighting has engulfed towns in South Sudan’s Equatoria region, where fleeing civilians report government troops turning up and embarking on killing sprees, including the slitting of civilians’ throats.

Owusu said other humanitarian workers were being “harassed across the country and humanitarian compounds and supplies have been looted and vandalized”.

Aid supplies had been looted in the Jonglei, Kajo-Keiji, Yei, Wau Shilluk and Mayendit areas in February and March.

Britain has said the scale of killings in South Sudan amount to genocide although the United Nations has yet to make such a determination.