Renewed violence in war-torn South Sudan is hindering humanitarian assistance to thousands of people displaced by the conflict. The International Organization for Migration (IOM) made the remarks following deadly clashes in Wau Shilluk, Upper Nile area, at the weekend.

"Violence in Upper Nile has once again hindered the ability of IOM and other relief agencies to provide assistance to populations seriously in need," said IOM South Sudan Chief of Mission, William Barriga. "Civilians will undoubtedly suffer as sporadic fighting makes it more difficult for aid workers to deliver services."

The organisation added that clashes between government and opposition forces – which started on 25 January and continued throughout the weekend – forced everyone to evacuate and stopped the agency from registering between 2,000 and 3,000 people to receive supplies.

Clashes reached Malakal, once one of South Sudan's largest urban areas and now a "largely deserted" area, according to the United Nations. The town is now home to more than 33,000 internally displaced persons (IDPs).

South Sudan descended into war in 2013 – just two years after gaining independence from Sudan – when President Salva Kiir, of the Dinka ethnic group, fired his deputy and rebel leader Riek Machar from his cabinet.

Ethnic-related violence targeting Dinka and Nuer ethnic groups then spread. An estimated 50,000 people have been killed, amid allegations of crimes against humanity committed by both sides, including rape, torture and the use of child soldiers. Millions are displaced and are facing severe food shortages due to a man-made famine.

Kiir and Machar have agreed on several peace deals – the last of which was signed in August 2015 – but have failed to control their troops, who have broken every ceasefire since 2014.

Machar, who leads the opposing faction Sudan People's Liberation Movement-in-Opposition (SPLM-IO), fled South Sudan following deadly fighting in capital Juba in July.

He is currently in South Africa, where he said he is seeking medical treatment, but in an exclusive talk with IBTimes UK said he was ready "to go home".

His wife, Angelina Teny, also a member of SPLM-IO, told IBTimes UK she believes her husband can contribute to achieve peace in the war-torn nation, which is on the verge of a Rwanda-style genocide.