Omaima A had travelled to Syria in January 2015 with her three underaged children.

German prosecutors said Monday they have arrested a German-Tunisian woman, the widow of a German rapper turned ISIS fighter, over her alleged membership of the terrorist group.

The woman, named only as Omaima A, was arrested in Hamburg last week and also stands accused of having raised her children in the ideology of the terrorist group.

Omaima A had married rapper Denis Cuspert -- who went by the stage name Deso Dogg -- after her first husband was killed in an air raid in Kobane, according to prosecutors.

Cuspert, killed last year in an airstrike in Syria, was one of the most notorious Western fighters for ISIS, having appeared in several propaganda videos including one that apparently showed him with a man's severed head.

Omaima A had travelled to Syria in January 2015 with her three underaged children, to join her first husband and their father, Nadar H, in Syria.

She lived under ISIS rules, raising her children following the group's doctrines, and receiving monthly financial help from the terrorist outfit, prosecutors said.

She subsequently wed Cuspert, but left him and returned to Germany pregnant with their child, as well as her three other children, in 2016.

According to German media, Omaima A quietly slipped back into German society after her return to Europe, working as an event manager and interpreter.

But a Lebanese journalist broke her story in April, sparking outrage in Germany over why the alleged ISIS member had not faced prosecution back in her home country.

Germany has put on trial several returning ISIS terrorists, and in April also took its first female returnee to court.