Hollande indirectly suggested that the Boko Haram group may have had a role in the Tuesday kidnapping. French Minister Laurent Fabius said it "probably was this sect Boko Haram."
Details of the kidnapping were not immediately clear.
Hollande, speaking during a visit to Greece, warned French citizens in the region "to avoid exposing themselves."
A French official close to the embassy in Cameroon said the group was believed to have been taken from northern Cameroon to Nigeria, where on Monday a little-known extremist group claimed responsibility for a separate abduction of seven foreigners.
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