President Donald Trump has announced US travel bans on citizens from 12 countries he has deemed "out of control."
Citizens of a further seven countries will face partial travel restrictions when the new policy comes into effect on Monday.
The travel ban applies to people from Afghanistan, Myanmar, Chad, the Republic of Congo, Equatorial Guinea, Eritrea, Haiti, Iran, Libya, Somalia, Sudan and Yemen.
And citizens of Burundi, Cuba, Laos, Sierra Leone, Togo, Turkmenistan and Venezuela will be subject to revised restrictions.
Speaking in the Oval Office earlier on Thursday, Trump said the new restrictions "can't come soon enough," citing national security concerns.
Since returning to the White House in January, Trump has launched an unprecedented campaign of immigration enforcement that has pushed the limits of executive power and led to clashes with federal judges trying to restrain the administration.
The travel ban results from a 20 January executive Trump signed requiring the departments of State and Homeland Security and the Director of National Intelligence to compile a report on "hostile attitudes" toward the US.
The aim is to "protect its citizens from aliens who intend to commit terrorist attacks, threaten our national security, espouse hateful ideology, or otherwise exploit the immigration laws for malevolent purposes," the administration said.
In a video released on social media, Trump tied the new ban to a terror attack on Sunday in Colorado, saying it underscored the dangers posed by some visitors who overstay their visas.
The suspect in that attack is from Egypt, a country that is not on Trump's restricted list. The Department of Homeland Security says he overstayed a tourist visa.
Trump said nationals of countries included in the ban pose "terrorism-related" and "public-safety" risks, as well as risks of overstaying their visas. He also said some of these countries had "deficient" screening and vetting or have historically refused to take back their own citizens.
His findings rely extensively on an annual Homeland Security report of visa overstays of tourists, business visitors and students who arrive by air and sea, singling out countries with high percentages of remaining after their visas expired.
"We don't want them," Trump said.
The inclusion of Afghanistan on the list has angered some supporters who have worked to resettle its people.
The ban makes exceptions for Afghans on Special Immigrant Visas, generally people who worked most closely with the US government during the two-decade war there.
The list can be changed, the administration said in a document circulated on Wednesday evening, if authorities of designated countries make "material improvements" to their own rules and procedures.
New countries can be added "as threats emerge around the world."
Reactions to the ban
International aid groups and refugee resettlement organisations have roundly condemned the new ban.
"This policy is not about national security — it is about sowing division and vilifying communities that are seeking safety and opportunity in the United States," said Abby Maxman, president of Oxfam America.
The African Union Commission expressed concern about the "the potential negative impact" of the ban on educational exchanges, business ties and broader diplomatic relations.
"The African Union Commission respectfully calls upon the U.S. administration to consider adopting a more consultative approach and to engage in constructive dialogue with the countries concerned," the commission said in a statement.
The Council on American-Islamic Relations, the country's largest Muslim civil rights and advocacy group, called the order "unnecessary, overbroad and ideologically motivated."
