FRANKFURT AM MAIN (AFP) - A woman believed to have belonged to the so-called Islamic State in Iraq and Syria (ISIS) group and her three children have arrived back in her home country Germany, police told AFP on Sunday (Nov 24).

The woman is the first adult female ISIS member to have been returned through official channels to Germany from Syria.

Named only as Laura H., the 30-year-old from Hesse state arrived at Frankfurt airport late on Saturday on a flight from from Erbil, Iraq.

While Laura H. was not immediately arrested on arrival, she remains the subject of an investigation on suspicion of membership of a terrorist organisation as well as failure to properly care for her children, news weekly Der Spiegel reported, citing security sources.

Her passport has been confiscated and she has been banned from leaving the country, while her children are being entrusted to a close relative, Spiegel added.

According to the magazine, she travelled in 2016 from Giessen in central Germany to Syria with her children and her husband, a Somalia-born US citizen, where she joined ISIS.

She had already been linked to Salafist (Islamic fundamentalist) circles in Germany and allegedly posted an online call for aid donations for Syria that in reality went to a fundamentalist group.

Following her husband's reported killing and her own capture by Kurdish security forces, Laura H. claims to have turned away from ISIS ideology.

A US aid organisation helped bring her to Erbil from the Al-Hol prison camp in north-eastern Syria, Spiegel reported.

Kurdish authorities have repeatedly urged Western countries to repatriate their nationals linked to ISIS, but they have been largely reluctant to do so.

A Turkish invasion of northern Syria last month sparked concern of a mass breakout from Kurdish-held jails and camps.

Germany had already brought home a handful of orphans, but no adults until Saturday.

Austria, Belgium, Britain and France have also repatriated some orphaned children, while the United States has repatriated several women and their children.

An Albanian boy taken by his mother to join ISIS in Syria returned to his home in Italy earlier this month.

Kazakhstan, Uzbekistan and Kosovo have all repatriated dozens of women and children.