Leonora, the German woman says she first came to Syria aged 15, just two months after converting to Islam

Four years after leaving Germany to live under the ISIS group, 19-year-old Leonora has fled the terrorists' last bastion in eastern Syria and says it's time to go home.

"I was a little bit naive," she says in English, wearing a long billowing black robe, and a beige headscarf with white spots.

US-backed forces are fighting the last ISIS terrorists in a final shred of territory in eastern Syria near the Iraqi border, causing thousands of people to flee.

Just beyond the frontline village of Baghouz, Leonora and her two small children are among the thousands of men, women and children to have scrambled out this week.

The young German woman says she first came to Syria aged 15, just two months after converting to Islam.

"After three days, I married my German husband," she tells AFP, at a screening centre for the displaced run by the US-backed Syrian Democratic Forces.

Leonora says she became the third wife of German terrorist Martin Lemke, after he travelled to Syria with his first two wives.

ISIS had the year before swept across large swathes of Syria and neighbouring Iraq, declaring a "caliphate" in areas it controlled.

Leonora first lived in the terrorist group's de-facto Syrian capital of Raqa, but says she was just a housewife.

Leonora says she became the third wife of German terrorist Martin Lemke

"I was just at home, in (the) house cooking, cleaning -- stuff like this," says the pale faced German, clutching the youngest of her two children, an infant aged just two weeks.

'Change House Every Week'

Syria's Kurdish authorities hold hundreds of foreign alleged ISIS fighters in detention, as well as thousands of their wives and children in camps for the displaced.

The Kurds have repeatedly urged Western governments to take back their nationals, but these powers have been reluctant.

At first life in Raqa was easy, Leonora says, but that changed when the SDF started advancing against the terrorists, with support from US-led coalition air strikes.

The Kurdish-led SDF overran Raqa in 2017, after years of what residents described as ISIS's brutal rule, which included public beheading and crucifixions.

"Then they lose Raqa, and we started to change our house every week because they lost every week a city," she says.

When they came under attack by the Kurdish-led SDF, Leonora says the ISIS fighters left their families to fend for themselves.

"They left the women alone, no food, they don't care about you," she says. The enemy was advancing "and you were sitting alone in an empty city with your kids".

They ended up in a tiny patch on the eastern banks of the Euphrates in Deir Ezzor province.

The SDF have cornered ISIS into a patch of less than four square kilometres in recent days.

'Big, Big Mistake'

Eventually, she says, she picked up her children, and fled with her husband, and his second wife into SDF-held territory.

US-backed forces detained Lemke on Thursday.

Leonora claims Lemke worked mostly as a technician for ISIS.

"He makes technical stuff, computer stuff, repairs computer, mobiles," she says.

But investigations published in German newspapers portray Lemke, who is now believed to be 28, as an influential figure among foreign terrorists in Syria.

More than 36,000 people have fled the SDF assault on the so-called "Hajin pocket" since early December, according to the Syrian Observatory for Human Rights, a Britain-based war monitor that relies on a network of sources inside the country.

Among them, 3,200 have been detained as alleged terrorists.

On arid farmland near Baghouz, a group of men sit on the ground as SDF and coalition personnel stroll nearby.

Not far off, a group of women and their children -- most from neighbouring Iraq -- wait to be driven north to a Kurdish-held camp for the displaced.

After four years under a now near-extinct ISIS caliphate, Leonora says she wants to go home.

"I want to go back to Germany to my family, because I want my old life back," she says.

"Now I know that it was a big, big mistake."