Two Americans who were captured in Syria and are accused of supporting the Islamic State (IS) group have been transferred back to the United States.

The Syrian Democratic Forces, a US-backed Kurdish ground force that has been fighting IS across parts of northern and eastern Syria, picked up the two detainees.

"Two US citizens, charged in separate cases with federal violations, have been transferred from the custody of the Syrian Democratic Forces to US custody and transported to the US where they will soon appear in federal courts," US Department of Justice spokesman Wyn Hornbuckle said on Tuesday.

Defendant Ibraheem Izzy Musaibli, 28, of Dearborn, Michigan is due to be arraigned in federal court in Detroit on Wednesday on charges of helping IS from April 2015 to June 2018.

The New York Times said last week that Musaibli was captured by the SDF in northern Syria earlier in July as he tried to escape the Middle Euphrates river valley, where the SDF has been working to drive IS militants from one of the last areas they control.

"The indictment alleges that, for a substantial period of time, defendant Musaibli provided material support to ISIS, one of the most violent terrorist organisations in the world," US Attorney Matthew Schneider said in a statement, using a different acronym for IS.

"We will vigorously prosecute anyone who provides, or even attempts to provide, support to terrorists."

It was not immediately known if Musaibli had an attorney.

Samantha Elhassani, meanwhile, has been charged in Indiana with making false statements to the FBI.

She accompanied her four minor children to Syria and lived in the IS-held capital of Raqqa for more than two years, reports said.

All the children are US citizens now in the custody of the Indiana Department of Child Services, said the Justice Department.

"Indiana DCS will make any necessary determinations regarding their custody, safety and well-being," it said.

In March, in an interview with the BBC while in detention in Syria, Elhassani said that her husband, a Moroccan national, tricked her into travelling to Raqqa.

Elhassani's son appeared in IS propaganda videos and her husband was an IS sniper before he was killed in a drone strike, according to reports.

Elhassani is due in court for an initial hearing at an unconfirmed date.

Commander Sean Robertson, a Pentagon spokesman, said the Defence Department provided aircraft and aircrew to fly the detainees from Syria to the United States.

US officials have previously said that the SDF has captured hundreds of IS fighters, many of them from other countries that have little or no interest in allowing them to return home.