As our helicopter approaches Leer in northern South Sudan, all one can see is eerily empty, dry, sun-stricken land. The people we meet on the ground, however, have a different story to tell. It is one of human suffering on an unimaginable scale.

Ten aid workers who were detained while on an assessment mission near Yei, Central Equatoria, have been freed. The humanitarian workers were held by an armed opposition group in South Sudan for more than five days, since 25 April.   

A surge in violent clashes in Unity, Jonglei and Central Equatorias is having a devastating impact on thousands of civilians and on humanitarian agencies trying to provide desperately needed assistance to vulnerable people.