A suicide bomber killed himself outside the French Embassy on Saturday night, wounding two embassy guards and a woman in the street, police and witnesses said.
The man blew himself up about 7 p.m., a policeman at the scene said. He confirmed witness accounts that the young man was dark-skinned and appeared young. He gave no other details. The policeman did not give his name, saying he was not allowed to talk to journalists.
Witnesses said the bomber's body was scattered in pieces on the street.
Extremist violence in Mauritania, a moderate Muslim nation in West Africa, has increased in recent years.
Earlier this month, a judge charged three men with murder in the slaying of an American teacher in Mauritania, and also charged them with aiding al-Qaida, which had claimed responsibility for the murder.
Mauritania's new president Mohamed Ould Abdel Aziz, who was sworn in three days before the bombing, said during his campaign that he would crack down on al-Qaida. He was elected in July after agreeing to elections after heading a coup in 2008.
The U.S. has expressed concern over the steady spread south from Algeria in recent years of al-Qaida's North Africa branch. While Washington never recognized Aziz's junta, it is keen to maintain Mauritania as a bulwark against the terror group and prevent the moderate Muslim nation from sliding toward extremism.