This marked the second Mauritanian Army attack on an AQIM base in Mali. In August, Mauritanian troops, backed by French advisers, raided an AQIM base just inside Mali and killed up to 10 insurgents.

Mauritania, which receives French and U.S. military assistance, said 12 AQIM fighters and six soldiers were killed in the latest fighting. The Defense Ministry said the operation began on Sept. 17 and continued into the next day.

Officials said the operations marked a campaign to find and release Westerners held prisoner by AQIM. Al Qaida has been accused of abducting at least five French nationals and holding them in northern Mali.

The operation took place one day after AQIM was believed to have abducted a French national in Niger. The Frenchman, an employee of the nuclear company Areva, and his wife, were believed to have been taken to Mali.

The French Foreign Ministry said French troops did not participate in the latest operation against AQIM. The French ministry said the Sept. 17 raid was not connected to the abduction of French nationals.

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