US President Donald Trump announced Wednesday evening a ban that is set to prohibit travel to the US from a dozen countries, alleging security risks.

Trump issued the directive in a presidential proclamation and an accompanying video message in which he said a recent attack on a march for Israeli hostages in Gaza in Boulder, Colorado "has underscored the extreme dangers posed to our country by the entry of foreign nationals who are not properly vetted, as well as those who come here as temporary visitors and overstay their visas."

The Trump's order specifically prohibits people from Afghanistan, Myanmar, Chad, the Republic of the Congo, Equatorial Guinea, Eritrea, Haiti, Iran, Libya, Somalia, Sudan and Yemen from entering the US.

Countries on partial restrictions

An additional seven countries -- Burundi, Cuba, Laos, Sierra Leone, Togo, Turkmenistan and Venezuela -- will face partial restrictions.

There have been fears of the travel bans since Trump’s return to the presidency in January. He had imposed a similar raft of measures during his first term from 2017 to 2021.

"Very simply, we cannot have open migration from any country where we cannot safely and reliably vet and screen those who seek to enter the United States," he said in the video.

"The strength of the restrictions we're applying depends on the severity of the threat posed. The list is subject to revision based on whether material improvements are made, and likewise, new countries can be added as threats emerge around the world, but we will not allow people to enter our country who wish to do us harm and nothing will stop us from keeping America safe."

It is set to take effect at 12.01 am Eastern Time on Monday.