Today's statement says the convoy was attacked Tuesday by "unknown armed gunmen" as it was returning from a field mission in Yirol East county.
The statement says IOM staff, health workers and civilians were the victims. Two people died of gunshot wounds, and an IOM health officer is in stable condition. The ambush took place in a region of South Sudan suffering from a cholera outbreak.
Famine has been declared in two other counties of South Sudan, which has been devastated by three years of civil war. The United Nations and aid groups have pleaded for more access amid numerous government restrictions.