French tourists were robbed at gunpoint and then shot dead with automatic weapons fire, claimed Mohamed Ould Lemine, the police chief of Aleg, the town 245 kilometers (150 miles) east of Mauritania's capital, Nouakchott, near where the incident occurred.
Authorities reported that five tourists had stopped on the side of the highway to have a picnic. Suddenly the gunmen approached them, demanding money.
The offenders took their money and then opened fire with automatic weapons. The robbers then whirled away in an old model Mercedes Benz.
The identities of the tourists have not been released.
An official from France's Foreign Ministry confirmed the deaths of the four French nationals. There was no any details about the incident.
Mauritania, three times the size of Arizona, is situated in northwest Africa with about 592 km of coastline on the Atlantic Ocean. It is bordered by Morocco on the north, Algeria and Mali on the east, and Senegal on the south. The country is mostly desert, with the exception of the fertile Senegal River valley in the south and grazing land in the north.