The Mauritanian news agency, Nouakchott Info, reported that, "Ely Ould Moktar, kidnapped on December 20 from his unit in Adel Begrou, is now free and is in good health."
The Associated Press reported that a security official said that the police officer was freed in exchange for a Malian who was serving five years in prison for aiding Al Qaeda in the Islamic Maghreb in the kidnapping of an Italian couple in 2009.
"He is not a member of AQIM but just an informer who facilitated the kidnapping of the Italian couple," a Malian military source was reported by AFP as saying.
The police officer, or gendarme, was taken only three miles from the Malian border.
Mali, Mauritania, Algeria and Nigeria face growing threats by AQIM, who regularly conduct terror attacks, drug trafficking and kidnappings in the vast desert shared by the four countries, making the area difficult to police.
In 2010, five French workers were kidnapped by AQIM and their whereabouts remain unknown.
In an attack last year, AQIM kidnapped a French aid worker and another French citizen. Both were killed by their captors after being pursued by French and Nigerien forces.