United Nations migration organization body IOM said on Wednesday it had suspended some of its screening services for Ebola after three of its aid workers were killed in South Sudan.

IOM South Sudan Chief of Mission Jean-Philippe Chauzy said the workers died during clashes between rival groups in the country’s central Equatorial region.

He said the organization had suspended screening for Ebola at five border points between South Sudan, Uganda and Democratic Republic of Congo, where an ongoing outbreak of the disease has killed thousands.

REUTERS