A 24-year-old Muslim convert has admitted taking her infant son to live among Islamic State terrorists in the Syrian city of Raqqa because she believes he will lead a 'better life' under their brutal regime.

Asiya Ummi Abdullah denied that children are unhappy living under the oppressive rule of ISIS' religious fanatics and explained that she felt her three-year-old son's spiritual well-being was better served in the group's de facto capital, where public crucifixions and beheadings are commonplace.

Ummi Abduallah - who had lived in Turkey since her teens but was born in Kyrgyzstan - said moving to the militant stronghold in Syria was in part to shield the young boy from the sex, crime, drugs and alcohol she sees as rampant in her home town Istanbul.

'Who says children here are unhappy?... He will know God and live under his rules,' she said.

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Missing: Sahin Aktan, 44, shows photos of his ex-wife Asiya Ummi Abdullah during an interview at his lawyer's office in Istanbul, Turkey. The 24-year-old Muslim convert took their child to territory controlled by ISIS

Radicals: ISIS supporters slogans as they carry the group's flags in front of the provincial government headquarters in Mosul, Iraq. A growing number of people are moving to the region to live under Shariah law

Ummi Abdullah's journey to radical Islam was born of loneliness and resentment.

Born Svetlana Hasanova, she converted to Islam after marrying Aktan six years ago. The pair met in Turkey when Hasanova, still a teenager, came to Istanbul from with her mother to buy textiles.

Ummi Abdullah had travelled from former Soviet republic Kyrgyzstan, where 80 per cent of the population are Muslim and Russian Orthodoxy is the minority religion.

Her story, told to The Associated Press in a series of Facebook messages, illustrates how the vast swaths of territory under the control of ISIS in Syria and Iraq have become home to thousands of devout Muslim families, despite the extreme violence so often found there.

Many of these highly religious families are Turkish and have made their way to ISIS' de facto capital Raqqa with young children in tow in order to live among murderers and terrorists.

'The children of that country see all this and become either murderers or delinquents or homosexuals or thieves,' Ummi Abduallah wrote, attempting to justify moving her young son into ISIS' brutal realm.

ISIS, the self-styled caliphate straddling Iraq and Syria, appears eager to attract families.

One recent promotional video shows a montage of Muslim fighters from around the world cuddling their children in Raqqa against the backdrop of an amusement park where children run and play.

Mr Aktan holds up a picture of the son he's not seen since July, when his ex-wife took him over the border to ISIS-controlled Raqqa where she now lives

A man, identified in the footage as an American named Abu Abdurahman al-Trinidadi, holds an infant who has a toy machine gun strapped to his back.

'Look at all the little children,' al-Trinidadi says. 'They're having fun.'

It may promote itself as a family-friendly place, but ISIS' bloody campaign for control of Syria and Iraq has uprooted hundreds of thousands of people in a wave of destruction involving brutal punishments and acts of cultural vandalism.

None of that matters to Ummi Abdullah.

'The blood and goods of infidels are halal,' she said - meaning she believes that Islam sanctions the killing of non-Muslims.

Ummi Abdullah's story has already made waves in Turkey, where her disappearance became front-page news after her ex-husband - a 44-year-old car salesman named Sahin Aktan - went to the press in an effort to find their child.

Many others in Turkey have carted away family to ISIS territory under far less public scrutiny and in much greater numbers.

In one incident earlier this month, more than 50 families from various parts of Turkey slipped across the border to live under ISIS, according to opposition legislator Atilla Kart.

Kart's figure appears high, but his account is backed by a villager from Cumra, in central Turkey, who told AP that his son and his daughter-in-law are among the massive group.

The villager spoke on condition of anonymity, saying he is terrified of reprisals.

The movement of foreign fighters to the Islamic State group - largely consisting of alienated, angry or simply war-hungry young Muslims - has been covered extensively.

The arrival of entire families, many but not all of them Turkish, has received less attention.

'It's about fundamentalism,' said Han, a professor of international relations at Istanbul's Kadir Has University. The Islamic State group's uncompromising interpretation of Islam promises parents the opportunity to raise their children free from any secular influence.

'It's a confined and trustable environment for living out your religion,' Han said. 'It kind of becomes a false heaven.'

'Before we were married': Aktan shows a picture of him and his wife in happier times, before the birth of their son and before her increasing interest in radical Islam

Aktan, speaking from his lawyer's office in Istanbul, said the relationship worked at first.

'Before we were married we were swimming in the sea, in the pool, and in the evening we would sit down and eat fish and drink wine. That's how it was,' he said, holding a photograph of the two of them, both looking radiant in a well-manicured garden. 'But after the kid was born, little by little she started interpreting Islam in her own way.'

Aktan said his wife became increasingly devout, covering her hair and praying frequently, often needling him to join in. He refused.

'Thank God, I'm a Muslim,' he said. 'But I'm not the kind of person who can pray five times a day.'

Asked why she became engrossed in religion, Aktan acknowledged that his wife was lonely.

But in Facebook messages to the AP, many typed out on a smartphone, Ummi Abdullah accused her husband of treating her 'like a slave.'

She alleged that Aktan pressured her to abort their child and said she felt isolated in Istanbul. 'I had no friends,' she said. 'I was constantly belittled by him and his family. I was nobody in their eyes.'

These photos are all Aktan has left of his son and ex-wife after she took the boy away to ISIS-controled territory

Aktan acknowledged initially asking his wife to terminate her pregnancy, saying it was too early in the marriage to have children. But when she insisted on carrying the pregnancy to term, Aktan said he accepted her decision and loved the boy.

Meanwhile Aktan's wife was finding the companionship she yearned for online, chatting with jihadists and filling her Facebook page with religious exhortations and attacks on gays.

In June, she and Aktan divorced. The next month, a day before her ex-husband was due to pick up their son for vacation, she left with the boy for Gaziantep, a Turkish town near the Syrian border.

Aktan, who had been eavesdropping on her social media activity, alerted the authorities, but the pair still managed to slip across the border

It isn't clear how many families have followed Ummi Abdullah's path, although anecdotal evidence suggests a powerful flow from Turkey into Syria.

In Dilovasi, a industrial town of 42,000 halfway between Istanbul and the port city of Izmit, at least four people - including a pair of brothers - recently left for Syria, three local officials said.

The officials, who spoke on condition of anonymity because they were not allowed to talk to the media, said that dozens of people from surrounding towns were believed to have left as well.

Aktan says he is in touch with other families in similar circumstances.

He cited one case in the Turkish capital, Ankara, where 15 members of the same extended family had left for Syria 'as if they're going on vacation.'

Even with U.S. bombs now falling on Raqqa, Ummi Abdullah says she has no second thoughts. 'I only fear God,' she wrote.

For Aktan, who says he hasn't seen his son since his ex-wife took the boy, her decision is a selfish form of fanaticism.

'If you want to die, you can do so,' he said. 'But you don't have the right to bring the kid with you... No one can give you this right.'

Ummi Abdullah's Facebook account has now disappeared.

Her messages to the AP were also removed, replaced with a message from Facebook saying they were 'identified as abusive or marked as spam.'