Judge blocks part of Trump immigration ban for stranded travelers

US President Donald Trump's order to restrict people from seven Muslim-majority countries from entering the United States sparked outrage before it hit a roadblock late on Saturday when a federal judge said stranded travelers could stay in the country.

The emergency court ruling was cheered at Boston's Logan International Airport, one of several major US airports where protesters angry with Trump's order gathered.

The American Civil Liberties Union (ALCU), which sought the temporary stay, said it would help 100 to 200 people with valid visas or refugee status who found themselves detained in transit or at US airports after Trump signed the order late on Friday.

"Victory!!!!!!" the ACLU, whose lawyers sued the government, tweeted after US District Judge Ann Donnelly issued her decision.

"Our courts today worked as they should as bulwarks against government abuse or unconstitutional policies and orders."

It was a dramatic end to Trump's first week in office, capped by the Republican president's four-month ban on refugees entering the US and a 90-day hold on travelers from Syria and six other countries.

Donnelly's decision to issue a temporary stay - which stopped short of ruling on the constitutionality of Trump's order - concerns dozens of people who were detained at US airports following Trump's actions. 

The exact number of those affected is unclear, but the judge ordered the government to provide lists of all those detained at US airports since the measure went into effect.

Sending those travelers back to their home countries after Trump's order would expose them to "substantial and irreparable injury," wrote Donnelly, who was appointed by Trump's Democratic predecessor Barack Obama.

Senior officials at the US Department of Homeland Security told reporters they had not seen the ruling, but said the government would implement any appropriate orders.