The US said it would suspend the issuance of visas that can lead to permanent residency for nationals of Nigeria, Eritrea, Kyrgyzstan, and Myanmar.
Sudanese and Tanzanian nationals will no longer be allowed to apply for “diversity visas”, which are available by lottery for applicants from countries with low rates of immigration to the US.
Mr Wolf said non-immigrant visas given to people for temporary stays – including visitors, those doing business or people seeking medical treatment – would not be impacted by the new rules.
Of the new nationalities facing visa restrictions, Nigerians account for the most immigration to the US.
In 2018 the US issued twice as many immigration visas to Nigeria than to the other five nations combined.
An official said the new measures were the result of failures by the six countries to meet US security and information-sharing standards.
“These countries, for the most part, want to be helpful but for a variety of different reasons simply failed to meet those minimum requirements that we laid out,” acting Homeland Security Secretary Chad Wolf told reporters on Friday.
He said officials would work with the countries on bolstering their security requirements to help them get off the list.
US President Donald Trump first introduced a travel ban in 2017. It currently closes US borders to citizens from seven countries, most of them with Muslim majorities.
In 2018 the US issued more than 8,000 immigration visas to citizens of Nigeria. That same year, just over 2,000 were issued to Sudanese nationals, 290 to Tanzanians, and just 31 to Eritreans.
The US had previously announced a ban on certain types of visas for Eritreans in 2017.