The Trump administration on Friday added six countries to the nations facing stringent travel restrictions, virtually blocking immigration from Africa’s most populous nation, Nigeria, and from Myanmar, where refugees are fleeing genocide.

Beside Nigeria, varying degrees of restrictions will hit three other African countries, Eritrea, Sudan and Tanzania, and one former Soviet state, Kyrgyzstan. Myanmar’s Muslim Rohingya could also be caught in the crossfire. The total number of countries on the restricted travel list now stands at 13.

Immigrant visas, issued mostly to foreigners intending to live in the United States, will be banned from Nigeria, Myanmar, Eritrea and Kyrgyzstan. The ban would prevent immigrants from Sudan and Tanzania from obtaining diversity visas. Homeland Security and State Department officials said some immigrants would be able to obtain waivers from the restrictions.