Families split, a father unable to reach his son's wedding and officials warning of a "gift to extremists" ─ American President Donald Trump's visa ban on seven Muslim countries has triggered shock and confusion among those affected.

Read more: Trump imposes sweeping restrictions on Muslim visitors

Trump this weekend signed an executive order that bans all immigrants and visa holders from seven Muslim-majority countries from entering the United States for 90 days, and opens the door to more country-based bans in future.

The seven countries mentioned in the order are Iran, Iraq, Syria, Libya, Somalia, Sudan and Yemen but its effects could extend well beyond barring newcomers from these countries.

It overhauls US refugee policy and initiates a fundamental shift in how the United States allows people to enter the country.

The US embassy in Baghdad said on Facebook that dual nationals from the seven countries would be barred from entering the United States, excluding those with American passports.

Trump's order follows through on one of his most controversial campaign promises to subject travelers from Muslim-majority countries to “extreme vetting” ─ which he declared would make America safe from “radical Islamic terrorists.”

Explore: Green card holders included in Trump ban: US Homeland Security

'Gift to extremists'

Iran's Foreign Minister Mohammad Javad Zarif said Sunday that Trump's move “will be recorded in history as a great gift to extremists and their supporters.”

“Collective discrimination aids terrorist recruitment by deepening fault-lines exploited by extremist demagogues to swell their ranks,” he tweeted.

His ministry said earlier that it would reciprocate with a ban on Americans entering the country, though it will not apply to those who already have a valid visa.

Explore: Tehran to ban Americans from entering Iran in tit-for-tat move

Meanwhile, Yemen's Houthi rebels, who control the capital Sanaa, also criticised the ban, stating: “All attempts to classify Yemen and its citizens as a probable source for terrorism and extremism is illegal and illegitimate.”

Yemenis made up the largest contingent ─ 12,998 ─ of immigrants to the US last year from the seven countries.

'I don't see freedom in the US'

Among thousands facing difficulties, an Iraqi family was barred in Cairo from taking their connecting flight to New York on Saturday.

“I had sold my house, my car, my furniture. I resigned from work and so did my wife. I took my children out of school,” Fuad Sharef, 51, told AFP.

Explore: 'At threat at any moment': Trump immigration ban dashes dreams of US-bound Iraqi family

“Donald Trump destroyed my life. My family's life. I used to think America was a state of institutions but it's as though it's a dictatorship,” he said.

An Iranian woman blocked from boarding at Tehran airport on Sunday said she had waited 14 years for her green card.

“Even during the hostage crisis at the US embassy (in 1980), the US government didn't issue such an order. They say the US is the cradle of liberty. I don't see freedom in that country,” she said, asking not to be named.

Mass hysteria in Irani community

With more than 1 million Iranians living in the United States, the restrictions have already caused chaos for students, businessmen and families.

"There is mass hysteria among the Iranian-American community ─ that's no exaggeration," said Saam Borhani, an attorney in Los Angeles.

He said clients were bombarding him with questions since Trump passed an executive order on Friday, suspending refugee arrivals and imposing tough controls on travellers from Iran, Iraq, Libya, Somalia, Sudan, Syria and Yemen.

“I have several clients impacted by the executive order ─ married couples whose spousal visas have been stopped, causing them to be separated. A father living in Iran who is unable to come to his son's wedding in California,” said Borhani, who was himself born in the US to Iranian parents.

US State Department figures show Iran accounted for around a quarter of the 31,804 visas granted to citizens from the seven countries last year.

'Trump's wall reaches Iran'

The situation has been complicated by a US federal judge, who ordered authorities on Saturday to stop deporting refugees and other travellers stuck at US airports.

“Uncertainty is the key word. Things are changing quickly and we're trying to keep people updated,” said Borhani, the lawyer in LA.

Getting a visa was already tough for Iranians, who had to travel to Turkey or the United Arab Emirates for the nearest US embassy.

BBC Persian reported that 9,000 Iranian asylum seekers were now blocked in Turkey.

After rising hopes under former president Barack Obama that relations between Iran and the US were improving, Trump has thrown everything back up in the air, Borhani said.

“I don't know what the future is going to hold, whether people here will be cut off permanently from their families in Iran. It's very stressful.”

Meanwhile, Iran's leading daily Hamshahri was headlined: “The United States has cut its relations with the Iranian people.”

Top reformist paper Shahrvand led with: “Trump's wall has reached Iran”.

'Difficult to remain silent'

Few anticipated the rally that developed almost at lightning speed at JFK airport over the weekend after Trump's executive order.

A small crowd of demonstrators at the city's far-flung John F. Kennedy Airport swiftly swelled into several thousand to decry the move to restricts refugees and travellers from seven Muslim-majority countries.

Alerted by social media and news reports, they held up homemade signs and chanted “Let them in!” late into the night.

Hanna Cowart sat out the January 21 “Women's March” that, a day after Trump's inauguration, saw millions take to the streets nationwide.

But now, the 21-year-old said, “it's becoming difficult for people to be silent.”

Even a federal ruling ordering authorities not to deport refugees and other travelers detained at airports could not soften the mood, with some demonstrators hurling verbal barbs at police who pushed protestors back to the sidewalks.

Private car driver Mousa Alreyashi traverses JFK every day, but on Saturday afternoon he decided to stop driving early and demonstrate for the first time.

“It's sending a message,” said the American citizen of Yemeni origin, who has been in the US for 20 years.

Alreyashi's mother, sister and brother remain in Yemen ─ one of the countries on Trump's list ─ with visa applications that have been pending for seven years.

He said “they were shocked” following the temporary ban: “it's like ordering food and in the middle of the delivery, people tell you now cannot deliver.”

'A national emergency'

“No hate, no fear, refugees are welcome here,” shouted demonstrators at JFK, some of them hoisting signs that read “We are better than this” and “Immigrants make America great.”

Despite having lived through the Vietnam War and protests against former presidents Ronald Reagan and George W. Bush, Christopher Gunderson called the current political landscape “the most serious situation in my lifetime.” “People are beginning to feel their power,” he said.

“It's possible that we're entering a very dark period, but the resistance so far has been heartening.”

Sister protests broke out at other airports nationwide including Washington, Chicago, Minneapolis, Denver, Los Angeles, San Francisco and Dallas.

“It's not surprising that people are mobilising,” said David Gaddis.

“It's not 1939. We have institutions,” the 43-year-old said. “People are prepared to stand against this.”

“Every day he's in office, it's a national emergency.”

In her Florida hometown, Cowart said many cast votes for Trump and did not understand the protests.

“They think we should accept it because he's the president,” she said. “It's not going to happen. “