The United Nations Mission in South Sudan (UNMISS) said Tuesday three Russian crew members were killed and one injured when a helicopter on a U.N. mission crashed near Bentiu in Unity state.
U.N. spokesman Stephane Dujarric said the injured crew member is being treated at a Doctor's Without Borders hospital in Bentiu but did not give details of his condition.
The U.N. said the helicopter, which was chartered from a Russian company, was on a routine cargo flight from Wau, in Western Bahr el Ghazal, to Bentiu, when contact was lost in the early afternoon on Tuesday. The U.N. has launched an investigation to determine what caused the crash.
South Sudan army spokesman Philip Aguer said opposition forces shot down the helicopter, which he erroneously referred to as an airplane.
"The plane was shot by forces of Peter Gadet, that is forces of Riek Machar," Aguer told South Sudan in Focus. "It's squarely the responsibility of Peter Gadet, of the forces of Riek Machar."
Gadet is one of three South Sudanese on both sides of the conflict who were sanctioned by the United States and European Union earlier this year.
Gadet is accused of leading an attack on the town of Bentiu in April, in which more than 200 civilians were killed.
The deadly helicopter crash came hours after government and opposition delegates at peace talks in Addis Ababa agreed to a blueprint for implementing a cessation of hostilities agreement signed seven months ago.
It also comes a day after UNMISS and the Intergovernmental Authority on Development (IGAD), the lead broker in South Sudan's peace process, announced that a ceasefire monitor died near Bentiu after he and five other monitors were detained by opposition forces.