The State Department issued a travel advisory warning of the risks of traveling to Nigeria.
"Violent crime committed by individuals and gangs, as well as by persons wearing police and military uniforms, remains a problem throughout the country," the advisory read.
Abuja in December declared a state of emergency in parts of the country because of militant activity attributed to Islamist militant group Boko Haram.
The advisory noted that Boko Haram took responsibility for a series of attacks in February that killed dozens of people and left many more injured. The group seeks to establish an Islamist state in a country divided along Muslim and Christian lines.
The State Department said kidnapping remains a security concern as well. Five U.S. citizens were kidnapped in Nigeria last year and another was abducted from his vehicle in January.
The advisory said foreigners shouldn't travel to areas designated as conflict areas by the government as Abuja may likely consider such activity illegal.
"The state of emergency gives the government sweeping powers to search and arrest without warrants," the State Department warned.