NEW YORK 

South Sudan has expelled a senior UN official in charge of monitoring the delivery of humanitarian aid, a UN spokesperson said Monday.

Secretary-General Ban Ki-moon condemned the expulsion of Toby Lanzer, who serves as his deputy envoy and resident aid coordinator in the war-torn country, Farhan Haq told reporters in New York.

"Mr. Lanzer has been instrumental in addressing the increasing humanitarian needs of conflict-affected communities in the country, and ensuring that life-saving humanitarian assistance reaches the most vulnerable," Haq said, urging South Sudan to reverse its decision.

"[Ban] further urges the government to cooperate fully with all United Nations entities present in South Sudan," Haq added.

South Sudan has been ravaged by violence since December of 2013, when President Salva Kiir accused his sacked vice-president, Riek Machar, of leading a coup attempt against his regime.

The ensuing conflict has left tens of thousands of people dead, 2 million seeking refuge – both internally and in neighboring countries – and 2.5 million at risk of starvation in 2015, according to UN data.

Renewed violence in northern Unity and Upper Nile recently resulted in the withdrawal of several aid agencies, leaving vulnerable communities without desperately needed humanitarian assistance.