President Trump on Wednesday signed a proclamation barring travelers and immigrants from a dozen countries and restricting the entry of nationals of another seven nations, citing concerns about national security.

Mr. Trump's proclamation fully bans the entry of foreigners from Afghanistan, Myanmar, Chad, the Republic of the Congo, Equatorial Guinea, Eritrea, Haiti, Iran, Libya, Somalia, Sudan and Yemen. With certain exemptions, Mr. Trump's order bans citizens of those countries seeking to come to the U.S. permanently as legal immigrants, as well as temporary visa holders, like tourists.

The president also partially suspended the entry of travelers and immigrants from Burundi, Cuba, Laos, Sierra Leone, Togo, Turkmenistan and Venezuela. That part of his proclamation applies to all prospective immigrants from these countries with visas to settle in the U.S. permanently and certain temporary visa holders.

The ban is set to take effect at 12:01 a.m. on Monday, June 9. 

Mr. Trump said the sweeping entry restrictions were necessary to address concerns related to terrorism in the countries listed in the order, inadequate vetting of the affected nationals and the lack of cooperation on deportations among some of the nations.

Mr. Trump's decree contains certain exemptions, including for U.S. permanent residents, Afghans who assisted American forces and have special visas, diplomats, athletes and dual nationals with a passport from a country not listed in his proclamation.