The U.S. embassy in Nigeria warned American citizens of a possible "terrorist threat" against U.S. 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.

• U.S. 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.

-Writing by MacDonald Dzirutwe, Editing by Sharon Singleton/Reuters