The fallout from President Donald Trump's immigration crackdown widened as residents and visa-holders from seven Muslim-majority countries who had left the United States found they could not return for 90 days.

It was a period of limbo for an unknown number of non-American citizens from Iraq, Syria, Iran, Sudan, Libya, Somalia or Yemen now barred from the country where they were studying or had lived, perhaps for years.

A federal law enforcement official who confirmed the temporary ban said there was an exemption for foreigners whose entry is in the US national interest. It was not immediately clear how that exemption might be applied.

READ: UK Prime Minister Theresa May declines to criticise US immigration ban

Mr Trump's order exempts diplomats and those already in the US with a visa or green card will be allowed to stay.

Airlines were being notified by Customs and Border Protection about passengers they needed to prevent from flying.

Mr Trump's order barred all refugees from entering the US for four months, and indefinitely halted any from Syria. He said the ban was needed to keep out "radical Islamic terrorists".

Lawsuits filed

Two Iraqis with ties to US security forces who were detained at New York's JFK Airport today are the first to file legal challenges against the ban.

In a lawsuit filed in federal court in Brooklyn, New York, the men are challenging the directive on constitutional grounds. The suit says that their connections to the American forces made them targets in their home country and the pair had valid visas to enter the United States.

READ: Donald Trump bars door to Muslim refugees

The plight of one of the men, a former US Army interpreter, is especially compelling, said David Leopold, a former president of the American Immigration Lawyers Association who is not involved in the suit.

"Here is a guy who was a translator who worked for the US military for years who himself was targeted by terrorists," he said. "It is clear that if he is sent back, he facing a direct threat to his life."

That man, Hameed Khalid Darweesh, was released later today and told a crowd of reporters outside John F. Kennedy International Airport that he did not have ill feelings about his detention.

"America is the greatest nation, the greatest people in the world," he said.

Darweesh, 53, worked for the US Army and for a US contractor in Iraq from 2003 to 2013 as an interpreter and engineer, the lawsuit said.

The second plaintiff, Haider Sameer Abdulkhaleq Alshawi, 33, was still being held. He is the husband of an Iraqi woman who worked for a US contractor in Iraq, and she already lives in Houston, the suit said.

Iran says it will reciprocate

Iran's foreign ministry announced it will limit issuing visas to American tourists in retaliation against the immigration crackdown.

The official IRNA news agency carried a statement by the Iranian foreign ministry saying Iran will resort to "counteraction" to Mr Trump's executive order.

The statement said: "Iran, to defend the dignity of the great Iranian nation, will implement the principle of reciprocity until the removal of the insulting restriction against Iranian nationals."

The statement adds: "It will apply corresponding legal, consular and political actions."

The two countries have had no diplomatic relations since 1979 when militants stormed the US embassy.

Silicon Valley concerned

Google CEO Sundar Pichai said in an email to staff that more than 100 Google employees were affected by the order, according to a Google executive. One Google employee of Iranian nationality with legal US residency made it back to the United States just hours before the order took effect, the executive said.

"We're concerned about the impact of this order and any proposals that could impose restrictions on Googlers and their families, or that could create barriers to bringing great talent to the US," Google, part of Alphabet Inc, said in a statement. "We'll continue to make our views on these issues known to leaders in Washington and elsewhere."

Microsoft said in a statement, "We share the concerns about the impact of the executive order on our employees from the listed countries, all of whom have been in the United States lawfully, and we're actively working with them to provide legal advice and assistance."

Facebook had no comment beyond a Friday blog post from CEO Mark Zuckerberg, in which he said he was "concerned" about the order and voiced support for immigrants.

Immediate suspension

The president's order immediately suspended a programme that last year resettled in the US about 85,000 people displaced by war, political oppression, hunger and religious prejudice.

Mr Trump indefinitely blocked those fleeing Syria, where a civil war has raged, and imposed a 90-day ban on all immigration to the US from the seven Muslim-majority nations.

"We want to ensure that we are not admitting into our country the very threats our soldiers are fighting overseas," he said as he signed the order at the Pentagon. "We only want to admit those into our country who will support our country and love deeply our people."

Mr Trump said the halt in the refugee programme was necessary to give agencies time to develop a stricter screening system.

While the order did not spell out what additional steps he wants the departments of Homeland Security and State to take, the president directed officials to review the refugee application and approval process and find any more measures that could prevent those who pose a threat from using the refugee programme.

The US may admit refugees on a case-by-case basis during the freeze, and the government will continue to process requests from people claiming religious persecution, "provided that the religion of the individual is a minority religion in the individual's country".

The State Department said the three-month ban in the directive applied to Iraq, Syria, Iran, Sudan, Libya, Somalia and Yemen - all Muslim-majority nations.

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

"There is no evidence that refugees - the most thoroughly vetted of all people entering our nation - are a threat to national security," said Lena Masri, the group's national litigation director. "This is an order that is based on bigotry, not reality."

During the past budget year, the US accepted 84,995 refugees, including 12,587 people from Syria. President Barack Obama had set the refugee limit for this budget year at 110,000.

According to Mr Trump's executive order, he plans to cut that to 50,000.
The International Rescue Committee called the suspension of the refugee resettlement programme a "harmful and hasty" decision.

US leading 'a race to the bottom' - NRC

IRC President David Miliband said: "America must remain true to its core values. America must remain a beacon of hope."

Mr Miliband praised the United States' record as a resettlement destination and said: "This is no time for America to turn its back on people ready to become patriotic Americans."

The head of a leading refugee aid agency said the ban hurts innocents fleeing violence.

Jan Egeland, of the Norwegian Refugee Council, said the decision "will not make America safer, it will make America smaller and meaner".

He said the decision dealt a "mortal blow" to the idea of international responsibility for those fleeing persecution.

The US is leading a "race to the bottom" in which politicians in wealthy countries provide "zero moral leadership", he said.

Malala Yousafzai, shot in the head by the Pakistani Taliban in 2012 to stop her campaigning for girls' education and co-winner of the 2014 Nobel peace prize, said she is heartbroken by the ban.

Ms Yousafzai implored Mr Trump "not to turn his back on the world's most defenceless children and families".

Refugees and immigrants, she said, have "helped build your country".