Prosecutors in Washington have charged a US citizen for joining the "Islamic State of Iraq and Syria" (ISIS) in Syria, according to a statement from the Justice Department Wednesday (September 16th).

The charges allege that Lirim Sylejmani conspired to provide and provided material support to ISIS, which the US classified as a terrorist organisation, between 2015 and 2019.

The department also claimed he received military training from the group.

"The defendant is a US citizen who abandoned the country that welcomed him to join ISIS in Syria," acting US Attorney Sherwin said in the statement of Sylejmani, who was born in Kosovo. "He will now be held accountable for his actions in an American courtroom."

Sylejmani was captured by the US-backed Syrian Democratic Forces (SDF) last year, according to the statement, before facing investigation by the FBI's Washington Field Office Joint Terrorism Task Force.

The question of how to handle captured foreign ISIS fighters has vexed Western governments, with the US vying for European countries to repatriate and try their own citizens.

Nations such as France and Britain reject the return of battle-hardened supporters of the ultra-violent ISIS group, which has claimed responsibility for a slew of grisly attacks against civilians.

Some European governments, including Britain, have revoked the citizenship of a number of citizens over alleged ISIS links.

But the US has pushed back against these approaches.

"Leaving them in the desert is not an effective solution. It makes it more likely they are going to find their way back to the battlefield, and accepting that risk is not being tough on terrorism," the US State Department's counterterrorism co-ordinator Nathan Sales told a meeting in Brussels last year.

Plus, it could put an undue burden on Middle Eastern countries already dealing with their own former ISIS-fighter citizens, according to the US.

The EU-backed Genocide Network this spring advocated that returning ISIS foreign fighters should be charged with war crimes under international law -- such as genocide or crimes against humanity -- in addition to whatever terrorism charges they may face at home.

As of May, some 2,000 fighters were still detained by Syrian forces and another 1,000 were in detention in Iraq, many of them European citizens mainly from France, Britain and Germany.

UK repatriates child from Syria

Britain said on Wednesday it had repatriated a child from Syria, one of dozens of British children thought to be trapped in the country.

Foreign Secretary Dominic Raab confirmed it on Twitter: "Pleased we have been able to bring home a British child from Syria."

"Safely facilitating the return of orphans or unaccompanied British children, where possible, is the right thing to do," he said.

The foreign ministry declined to provide further details when contacted by AFP, citing legal restrictions on reporting cases involving minors.

Charity Save the Children said in a report last year that more than 60 British children were stranded in north-east Syria.

Human rights group Reprieve estimates there are 14 adult women and eight men from Britain detained in camps or prison in the region, along with their children.

It noted the UK government was refusing to repatriate the women with children, "in stark contrast" to the actions of other governments, including the US.

"It (the government) needs to do the sensible thing and repatriate the remaining British families," the group's interim executive director, Maya Foa, added.

"Our justice and security systems are well-equipped to handle the small handful of British adults held in north-east Syria."

Save the Children has said the threat to children stranded in Syrian camps was high, and that eight youngsters aged under five died in just five days.

There are also fears of a deadly outbreak of the coronavirus.