The 3,050 lane metre Repubblica di Roma (built 1992) was near the Togolese capital of Lome when the incident occurred around 3pm.
A nearby utility boat arrived on the scene to see smoke billowing from a deck area near the stern of the ro-ro.
Eleven crew members evacuated the stricken vessel and boarded the African Princess 4 (built 1980), owned by London-based Top Fenders.
Grimaldi Lines operates the multipurpose vessel, which has a capacity for 1,000 containers, on a route between southern Europe and West Africa.
It is not clear how the fire started.
The Italian owner could not be reached for comment at the time of writing.
