From the U.S. State Department:
The U.S. Department of State warns U.S. citizens of the risks of traveling to Mauritania, and urges those who travel to Mauritania to exercise extreme caution because of activities by terrorist groups in the region, including al-Qaida in the Islamic Maghreb (AQIM). AQIM continues to demonstrate its intent and ability to conduct attacks against foreign nationals, including U.S. citizens. ...
U.S. citizens should consult the Country Specific Information sheet for the Republic of Mauritania and the Worldwide Caution, both located on the Department of State’s Bureau of Consular Affairs website. Follow us on Twitter and the Bureau of Consular Affairs page on Facebook as well. If you don't have internet access, current information on safety and security can also be obtained by calling 1-888-407-4747 toll-free in the United States, or for callers from other countries, a regular toll line at 1-202-501-4444. These numbers are available from 8:00 a.m. to 8:00 p.m. Eastern Time, Monday through Friday (except U.S. federal holidays).
U.S. State Department Warning