Five German women are in custody following a military operation in the Iraqi city of Mosul. It is alleged that they travelled to the embattled city to support the Islamic State terror group (IS), Deutsche Welle reports.

The five German women in remand are reportedly part of a group of 20 female fighters apprehended in Mosul's beleaguered ancient city last week, including other nationals from Russia, Turkey, Canada, Libya, and Chechnya.

An Iraqi military official told the newspaper that the group of women had been hiding in a system of tunnels built by IS, and that weapons and explosive belts were found at the site of their arrest - presumably to be used for assaults on Iraqi soldiers. Initial reports say that the arrested individuals were working for the police arm of IS.

Germany's daily "Die Welt" newspaper reported that a 16-year-old convert to Islam from Germany's federal state of Saxony was among those seized by local security forces. The girl had been missing for about a year after allegedly getting in touch with IS supporters online.

Authorities in Saxony's capital Dresden said that the underage girl had been under investigation for being involved in preparations for a violent act against the state, but that the probe had been suspended due to her absence.

Chief prosecutor Lorenz Haase told "Die Welt" that the investigation would be resumed when the girl was back in Germany.

More than 900 Islamists are believed to have travelled to Syria and Iraq from Germany to support IS, including several underage girls.