The young man, who has not been identified, was arrested Thursday and convicted of lack of respect for the prophet.
He will be given a chance to repent, but if he does not, he will face the death penalty, the report said.
The article was published on several websites and questioned the prophet's decisions during the holy wars.
Sharia law is enforced in Mauritania, but the death penalty has not been used since the 1980s.
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