The White House has denied an accusation from rights groups that it flouted due process by defying a judge’s order while carrying out deportations at the weekend.

A group of 238 alleged Venezuelan gang members, plus 23 alleged members of the international MS-13 gang, were sent from the US to a prison in El Salvador. Some were removed from the country under a law not invoked since World War Two.

The move came despite a temporary block issued by a judge. The White House said the judge’s order itself was not lawful and was issued after the group was deported.

Neither the US government nor El Salvador has identified the detainees, or provided details of their alleged criminality or gang membership.

Announcing the move on Saturday, the day after he signed it, Trump accused the gang Tren de Aragua (TdA) of “perpetrating, attempting, and threatening an invasion or predatory incursion against the territory of the United States”.

He cited the Alien Enemies Act – a piece of legislation that dates to 1798, which was designed to allow non-citizens to be deported in times of war or invasion. Campaigners have questioned Trump’s justification.

The act was used to process 137 of the total of 261 people who were deported, a senior administration official told CBS News, the BBC’s US partner.

The basis on which the other deportees were removed from the US remains unclear, and details of the group as a whole have not been disclosed.

Several relatives of men believed to be among the group told the New York Times that their loved ones did not have gang ties.

The case raises constitutional questions since, under the US system of checks and balances, government agencies are expected to comply with a federal judge’s ruling.

A hearing to ascertain more information about the Trump administration’s use of the Alien Enemies Act is scheduled for 16:00 EDT (20:00 GMT) on Monday.

The order to halt the deportations came from US District Judge James Boasberg on Saturday evening, who demanded a 14-day pause pending further legal arguments.

After lawyers told him that planes with deportees had already taken off, the judge reportedly gave a verbal order for the flights to turn back, although that directive did not form part of his written ruling.

White House press secretary Karoline Leavitt denied the court ruling had been broken.

“The administration did not ‘refuse to comply’ with a court order,” she said. “The order, which had no lawful basis, was issued after terrorist TdA [Tren de Aragua] aliens had already been removed from US territory.”

The justice department echoed Leavitt, saying the deportees had already left before the judge’s ruling – which it has appealed against.

But a timeline of events reported by US media suggests the Trump administration appears to have had the opportunity to stop at least some of the deportations.

• 17:25 EDT: A first flight believed to be carrying deportees leaves Texas, according to data from tracking site Flightradar24. Takeoff happens while a hearing held by Judge Boasberg is paused. Earlier that afternoon, the White House said Trump was invoking the Alien Enemies Act
• 17:44 EDT: A second flight believed to be carrying deportees leaves Texas, according to Flightradar24
• 18:05 EDT: Boasberg’s hearing resumes and the government declines to say if deportations are ongoing, according to ABC News
• 18:46 EDT: Boasberg orders the government to turn around the two planes if they are carrying non-citizens, according to ABC
• 19:26 EDT: Boasberg issues his written order for a temporary restraining order, according to ABC
• 19:36 EDT: A third flight believed to be carrying deportees leaves Texas, according to Flightradar24

Trump’s border tsar, Tom Homan, told reporters at the White House on Monday that Trump did “exactly the right thing”.

“The plane was already over international waters with a plane full of terrorists and significant public safety threats,” he said. “We removed terrorists. That should be celebrated in this country.”

El Salvador’s President Nayib Bukele confirmed the arrival of deportees. “Oopsie… Too late,” he said of the judge’s order, writing on social media. His team also published footage of some of the men inside one of its mega-jails.

Rights groups accused Trump of using a 227-year-old law to circumvent due process.

The American Civil Liberties Union (ACLU) questioned Trump’s use of a sweeping wartime authority which allows fast-track deportations. “I think we’re in very dangerous territory here in the United States with the invocation of this law,” said Lee Gelernt from the organisation.

The Alien Enemies Act only allowed deportations when the US was in a declared war with that foreign government, or was being invaded, Mr Gelernt said. “A gang is not invading,” he told BBC News.

The act was last used during World War Two to intern Japanese-American civilians.

Making matters worse was the fact “the administration is saying nobody can review what they’re doing”, Mr Gelernt added.

Meanwhile, Amnesty International USA said the deportations were “yet another example of the Trump administration’s racist targeting” of Venezuelans “based on sweeping claims of gang affiliation”.

Venezuela itself criticised Trump, saying he “unjustly criminalises Venezuelan migration”.

The latest deportations under Trump’s second term are part of the president’s long-running campaign against illegal immigration.

The US president has also moved to strengthen ties with El Salvador.

The two gangs targeted with the weekend deportations were declared “foreign terrorist organisations” by Trump after returning to the White House in January.