Passengers have been barred from flights into the US and visa holders refused entry after Donald Trump imposed strict new controls on travellers from seven Muslim-majority nations.

The US President, who had promised the measures - called "extreme vetting" - during last year's election campaign, said he was making America safe from "radical Islamic terrorists" as he signed the executive order on Friday.

The decree means no visas will be issued for 90 days to migrants or visitors from Iran, Iraq, Libya, Somalia, Sudan, Syria and Yemen.

Image: Protests are taking place at JFK airport in New York

A Homeland Security spokeswoman confirmed the order would also bar green card holders from those countries who had left the United States from returning for 90 days.

An official told the Associated Press that those already in the US with a visa or green card would be allowed to stay, while another said there was an exemption for foreigners whose entry was in the national interest.


Image: Protesters at the international arrivals area of Dulles Airport

Within hours, campaigners said there were reports of visa holders being denied permission to enter the country, and Congressmen were seen arriving at JFK to try and help some of those detained.

Demonstrations have broken out at the airport in New York - though late on Saturday afternoon Mr Trump declared the new rules were working out "very nicely".

Image: President Trump says the order is necessary to keep the US safe from terrorists

Google urged about 100 employees to return as soon as possible from abroad as they could be affected, while Facebook CEO Mark Zuckerberg said he was "concerned".

Cairo airport officials said six Iraqis and a Yemeni had been barred from an EgyptAir flight to New York following the order.

An Iraqi journalist living in the US, Mohammed al-Rawi, posted on Facebook that his father had been turned away from a Los Angeles-bound flight in Qatar.

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Dutch airline KLM says it has had to turn away seven would-be passengers, while Qatar Airways is advising passengers bound for the US from banned countries that they need to have either a green card or diplomatic visa to travel.

Canada's WestJet Airlines said it had turned back a passenger bound for the US in order to comply with the executive order.

Anthony Romero, executive director of the American Civil Liberties Union, said: "'Extreme vetting' is just a euphemism for discriminating against Muslims."

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The Council on American-Islamic Relations said it would challenge the constitutionality of the executive order.

A senior official from the Trump administration told Reuters it was "ludicrous" to call it a "Muslim ban".

They said the seven countries had been deemed "high risk" and that other largely Muslim countries such as Afghanistan, Malaysia, Oman, Pakistan, Tunisia and Turkey were unaffected.

Iran said it would ban Americans from entering the country in response to the "insulting" order.

Image: A letter from @AlabedBana to her friend in America

The new measures also suspended the entire US refugee resettlement programme for at least 120 days while tough new vetting rules of applicants' backgrounds are established.

The new protocols will "ensure that those approved for refugee admission do not pose a threat to the security and welfare of the United States".

In addition, it specifically bars Syrian refugees from the US indefinitely, or until the President himself decides that they no longer pose a threat.

The UN refugee agency and the International Organization for Migration called on Mr Trump to let in those fleeing war and persecution.

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"The needs of refugees and migrants worldwide have never been greater and the US resettlement programme is one of the most important in the world," the agencies said in a joint statement.

Canadian Prime Minister Justin Trudeau tweeted: "To those fleeing persecution, terror & war, Canadians will welcome you, regardless of your faith."

French foreign minister Jean-Marc Ayrault said: "This can only worry us, but there are many subjects that worry us."

Germany's foreign affairs minister Sigmar Gabriel said: "The United States is a country where Christian traditions have an important meaning. Loving your neighbour is a major Christian value, and that includes helping people."