Washington DC - US President Donald Trump signed a new travel ban Wednesday targeting 12 countries, including Afghanistan, Iran, and Yemen, reviving one of the most controversial measures from his first term.

Trump said the measure was spurred by a makeshift flamethrower attack on a Jewish protest in Colorado that US authorities blamed on a man they said was in the country illegally.

The move bans all travel to the US by nationals of Afghanistan, Myanmar, Chad, the Republic of the Congo, Equatorial Guinea, Eritrea, Haiti, Iran, Libya, Somalia, Sudan, and Yemen.

Trump also imposed a partial ban on travelers from seven countries: Burundi, Cuba, Laos, Sierra Leone, Togo, Turkmenistan, and Venezuela. Some temporary work visas from these countries will be allowed, however.

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The bans go into effect on Monday, the White House said.

"The recent terror attack in Boulder, Colorado, has underscored the extreme dangers posed to our country by the entry of foreign nationals who are not properly vetted," Trump said in a video message from the Oval Office posted on X.

"We don't want them."

The ban will not apply to athletes competing in the 2026 World Cup, which the US is co-hosting with Canada and Mexico, as well as the 2028 Los Angeles Olympics, Trump's order said.

The US leader compared the new measures to the "powerful" ban he imposed on a number of mainly Muslim countries in his first term, which caused travel disruption across the world.

Trump said that the 2017 ban had stopped the US from suffering terror attacks that happened in Europe.

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"We will not let what happened in Europe happen in America," Trump said.

"We cannot have open migration from any country where we cannot safely and reliably vet and screen."

Venezuela hit back by warning that the US itself was a dangerous destination.

"Being in the United States is a great risk for anyone, not just for Venezuelans," Venezuela's Interior Minister Diosdado Cabello said after the announcement, warning citizens against travel there.

Trump's new travel ban could, however, face legal challenges, as have many of the drastic measures he has taken in his whirlwind return to office.