The humanitarian group Doctors Without Borders says two of its workers have been killed in separate attacks in villages in South Sudan.

The group, also known by the French name Medecins Sans Frontieres, said Tuesday that Gawar Top Puoy, a logistician, and community health worker James Gatluak Gatpieny were killed last week in troubled Unity state.

MSF spokeswoman Victoria Russell said the area was inaccessible and the group only received confirmation of their deaths over the weekend. The exact circumstances were unclear.

South Sudan has been at war since a December 2013 rebellion by a former deputy president.

As fighting increased in May, the group evacuated international staffers from its hospital in Leer in Unity state. The two local workers joined their families in nearby swamps to avoid the violence.