The US embassy in Nigeria warned American citizens of a possible "terrorist threat" against US facilities and affiliated schools in the West African country in a security alert late on Monday.
The embassy has been on heightened alert since the U.S. and Israel launched coordinated strikes against Iran.
US citizens should take additional precautions when traveling to the embassy in the capital Abuja and the U.S. consulate in commercial capital Lagos and U.S.-affiliated schools, the embassy said.
The embassy did not give details on the security threat, but Nigerian authorities have in recent days stepped up security in Abuja following threats of pro-Iranian protests.
In northern Nigeria, where there is a sizeable Shi'ite Muslim minority influenced by Iran, thousands of protesters have taken to the streets to march in support of Iran.