Washington, Jan 29 (Agencies) : Hundreds of protesters gathered at airports in Dallas, Chicago, New York and elsewhere while inside, anxious family members waited and worried for travelers.

President Donald Trump's order for “extreme vetting” of visitors and legal U.S.residents from seven Muslim-majority countries sparked outrage and protests on Saturday with activists arguing in court to tryto block deportations of people stranded in U.S. airports.

The new Republican President on Friday put a four-month holdon allowing refugees into the United States and temporarily barred travelers from Syria and six other countries. Immigration lawyers, activists and Democratic politicians reacted furiously, and many worked to help marooned travelers find a way back home.

In Brooklyn, the American Civil Liberties Union sought to block the order in an emergency hearing, a large crowd chanting "Let them stay, it's the American way!” outside the courthouse.

Hundreds of protesters gathered at airports in Dallas, Chicago, New York and elsewhere while inside, anxious family members waited and worried for travelers.

At Chicago O'Hare International Airport, brothers Bardia and Ayden Noohi waited for four hours for their father Kasra Noohi -who has an Iranian passport and a U.S. green card - to be allowed through.

They knew Mr. Trump had pledged tougher rules but did not expect they would affect holders of green cards, which allow foreigners to live and work in the United States.

“I didn't thing he'd actually do it,” Bardia Noohi (32), said. “A lot of politicians just talk.”

Mr. Trump, who took office just over a week ago, had promised during his campaign what he called “extreme vetting” to do more to protect Americans from terror attacks.

He told reporters in the Oval Office that his order was “not a Muslim ban” and said the measures were long over due.

“It's working out very nicely. You see it at the airports, you see it all over,” Mr. Trump said.

“We're going to have a very, very strict ban and we're going to have extreme vetting, which we should have had in this country for many years.”

CHAOS

The ban affects travelers with passports from Iran, Iraq, Libya, Somalia, Sudan, Syria and Yemen. Green card holders will not be allowed back in until they are re-screened.

The order seeks to prioritize refugees fleeing religious persecution. In a television interview, Mr. Trump said the measure was aimed at helping Christians in Syria.

Confusion abounded at airports as immigration and customs officials struggled to interpret the new rules, with some legal residents who were in the air when the order was issued detained at airports upon arrival.

A chaotic scene played out in the arrivals terminal at John F. Kennedy International Airport in New York, where a group of lawyers had filed a lawsuit on behalf of two Iraqi men who had worked for the U.S. military who were in the air when Mr. Trump signed the order.

Thousands of refugees seeking entry were thrown into limbo. Melanie Nezer of the Hebrew Immigrant Aid Society, a Jewish group that works with refugees, said she knew of roughly 2,000 who were booked to come to the United States next week.

The U.S. technology industry, a major employer of foreignworkers, hit back on Saturday, with some leaders calling the order immoral and un-American.

Colleges also spoke out on behalf of students from the countries, and warned students in the United States that they should avoid travel lest they not be allowed back in.

Arab travelers in the Middle East and North Africa said the order was humiliating and discriminatory. It drew criticism from U.S. Western allies including France, Germany and Britain.

Iran condemned the order as an “open affront against the Muslim world and the Iranian nation” and vowed to retaliate. Of the seven countries targeted, Iran sends the most visitors to the United States each year - around 35,000 in 2015, according to the Department of Homeland Security.

Sudan called the action “very unfortunate” after Washington lifted sanctions on the country just weeks ago for cooperation on combating terrorism. A Yemeni official expressed dismay at the ban.

Canadians welcome those fleeing persecution, terror and war"regardless of your faith,” Prime Minister Justin Trudeau said in a Twitter post.

LEGAL RESIDENTS STUNNED

During the presidential campaign, Trump promised to clampdown on immigration as a way to prevent attacks. He first proposed a ban on Muslims entering the United States, modifying that later to “extreme vetting” of immigrants from certain countries.

It was unclear how many legal permanent residents would be affected. A senior U.S. administration official said on Saturday that green card holders from the seven affected countries have to be cleared into the United States on a case-by-case basis.

According to State Department guidance, travelers who have dual nationality of one of these countries will not be permitted for 90 days to enter the United States.

Legal residents of the United States were plunged into despair at the prospect of being unable to return to the United States or being separated from family members trapped abroad.

In Cairo, five Iraqi passengers and one Yemeni were barred from boarding an Egypt Air flight to New York on Saturday, sources at Cairo airport said. Dutch airline KLM said on Saturday it had refused carriage to the United States to seven passengers from predominately Muslim countries.

U.S. AGENCIES SCRAMBLE

In Washington, the agencies charged with handling immigration and refugee issues grappled with how to interpret the measure, and enforcement was uneven.

U.S. officials, speaking on condition of anonymity, said they were not consulted on the executive order and in some casesonly learned the details as they were made public.

At the State Department, a senior official said lawyers were working closely with their counterparts at Homeland Security to interpret the executive order, which allows entry to people affected by the order when it is in the “national interest.”

However, a federal law enforcement official said, “It's unclear at this point what the threshold of national interest is.”

Senior administration officials said it would have been "reckless” to broadcast details of the order in advance of new security measures. The officials told reporters that Homeland Security now has guidance for airlines.

“I don't think anyone is going to take this lying down," said Cleveland immigration lawyer David Leopold. “This is the tip of the spear and more litigation is coming.”