Pictures of a teenager being arrested by Iraqi police have been widely circulated on social media in the last few days. Although the girl’s identity is still unclear, it is thought she is Linda W, who left her hometown of Pulsnitz near Dresden last July.
The authorities managed to track her movements to Istanbul, after which the trail went cold.
A reporter for German newspaper Bild, Bjorn Stritzel, said on Twitter that according to his rebel sources Linda had been held in an area of Idlib province last August by Islamist rebels sympathetic to Isis before being smuggled to the so-called caliphate.
It is not clear when Linda – if she has been correctly identified – went to Mosul. The city has been under siege by US-backed Iraqi coalition forces since October 2016.
Fierce fighting and a US-led air campaign have killed thousands of civilians, and caused almost a million to flee their homes. While Iraqi Prime Minister Haider al-Abadi declared last week that Isis has been defeated, clashes continue in a tiny pocket of the Old City, and the authorities remain fearful of sleeper cell attacks.
Five German women who travelled to Syria and Iraq to join the caliphate have been captured by Iraqi security forces during Mosul's fall.
Foreign men who joined Isis were often put in frontline combat roles or used as suicide bombers during the brutal nine-month-long campaign to retake the city. Earlier this month, shocking footage emerged of a woman cradling a baby who then blew herself up to take out two nearby soldiers.
At least 27,000 foreigners are estimated to have travelled to Syria to take part in various sides of the fighting in the country’s six years of civil war.