The US Justice Department said Thursday (October 1st) that it brought home 27 Americans who went to Syria and Iraq to join the "Islamic State of Iraq and Syria" (ISIS), as Washington again urged other nations to do the same.

A day after filing charges against a Trinidadian-American father and son who enlisted in ISIS in 2015, the department said it had brought criminal terrorism support cases against some of those returning Americans.

Washington has said it is setting an example for other countries, notably Britain and France, who have resisted repatriating perhaps hundreds of their nationals from Iraq and Syria.

"This was our moral responsibility to the American people and to the people of the countries to which these terrorists traveled," said Assistant Attorney General John Demers in a statement.

The 27 represent only a portion of the hundreds of Americans and thousands of citizens of other countries who, often with their families, enlisted in ISIS as it undertook a bloody campaign to establish its "caliphate" across Syria and Iraq six years ago.

Many remain in camps in Syria under the control of the Syrian Democratic Forces (SDF).

Demers said they had repatriated all 27 "against whom we have charges", suggesting there could still be more, as cases are built against them. He did not offer details on the accusations.

Foreign fighters problem

After wrestling with whether to abandon US "foreign fighters" in the region or to move them to the US military's Guantanamo prison camp, Washington decided two years ago to try them in federal courts.

Those charged with "material support of a designated terrorist group" include Kazakhstan-born, naturalised US citizen Ruslan Maratovich Asainov, 44, who was called an ISIS sniper and weapons trainer.

Also charged was Texas-born Omer Kuzu, who as a 17-year-old went to Syria with his brother in 2014 and worked as an ISIS communications specialist before his capture last year.

Some US allies have balked at bringing home their nationals.

London has refused to try El Shafee Elsheikh and Alexanda Kotey, two men from Britain who are tied to murders of US and British journalists and aid workers as part of a notorious ISIS kidnapping cell dubbed The Beatles.

Instead, Washington is now preparing the transfer them to the US for trial.

Washington has been pressing hard the repatriation issue, vetoing on August 31st a UN resolution pushed by Indonesia on handling foreign fighters because it did not demand countries act to take back their own.

On Thursday, the State Department praised Italy for repatriating one of its citizens to stand trial for supporting ISIS.

"Repatriating and prosecuting terrorists is the most effective way to keep them from returning to the battlefield," Secretary of State Mike Pompeo said.