The AfDB lodged a formal complaint with Ethiopian authorities last month, calling the physical assault and hours-long detention of two of its employees on Oct. 31 a "very serious diplomatic incident".

The two sources were not aware of a timetable for the withdrawal of the Ethiopia-based employees.

Nor did they provide details on how the decision might affect the AfDB's operations in Ethiopia, where, according to the bank's website, it has eight projects worth a total of about $308 million.

An AfDB spokesman did not immediately respond to a request for comment on the staff pull-out.

At the time of its formal complaint, the AfDB said the Ethiopian authorities had promised to investigate, and Ethiopian state finance minister Eyob Tekalign said his government regretted the incident.

(Reporting by Joe Bavier and Rodrigo Campos; Editing by Rosalba O'Brien)