5. Nigeria

Two extremist groups, Boko Haram, and Islamic State West Africa, are responsible for much of the violence that occurs in Nigeria, and commonly target heavily populated areas like churches, schools, restaurants, hotels, and entertainment venues.

The U.S. Department of State says visitors "should be vigilant at public gatherings and locations frequented by foreigners," and to "Exercise extreme caution throughout the country due to the threat of indiscriminate violence."