PARENTS should lock up their children's passports if they fear that they are at risk of radicalisation, a charity has suggested, after three schoolgirls from London flew to Turkey, with the aim, it is believed, of joining Islamic State (IS).

Shamima Begum, aged 15, Kadiza Sultana, 16, and Amira Abase, 15, all pupils at Bethnal Green Academy, boarded a flight from Gatwick to Istanbul on Tuesday of last week. Police said on Wednesday that they had "reason to believe" that the girls had since managed to enter IS-held territory in Syria.

On Saturday, Sara Khan, the head of Inspire, a charity tackling extremism and gender inequality, told The Guardian: "Parents need help, and the most practical suggestion I can make is: keep your daughter's passport under lock and key."

Ms Khan published a letter on Monday, "to young Muslim girls, if you are considering leaving the UK to join ISIS". It warns: "You are being lied to through a gross manipulation of the teachings of our faith."

It is estimated that 500 Western women have migrated to IS-held territory. A study of their experiences, Becoming Mulan? Female Western migrants to ISIS, based on the social-media accounts of 12 women, was published last month by the Institute for Strategic Dialogue, a British think tank.

Excitement about building an "Islamic utopia", and delight at the barbarity inflicted on the enemy, is documented, alongside an inventory of the spoils of war, and reports on the pleasures of house-cleaning.

The study includes an exploration of the reasons for migration. The women talk "at length" about the oppression of Muslims by Western powers, and express a desire to fulfil their mandatory religious duty to build a Muslim caliphate and secure their place in heaven. The sense of camaraderie is strong: the researchers identified a "search for meaning, sisterhood, and identity".

The unmarried women live, free of charge, in a women's hostel, and receive monthly food supplies and an allowance. One woman describes receiving items seized from "the Kuffar" (non-believer), including microwaves, milk-shake machines, and vacuum cleaners.

Women are forbidden to engage in combat by IS; but those monitored in the report "revel in the gore and brutality of the organisation", and "indicate a desire to inflict violence themselves". One described a video of a beheading as "beautiful". The authors warn that "the most important risk is that the female migrants can inspire others, both men and women, to carry out attacks in Western countries, or to travel to Syria and Iraq."

The picture painted by the migrants is not entirely positive. Women speak of the difficulty of leaving their families behind, and there is some evidence that migrants are treated differently from the indigenous population. One woman describes how a migrant who experienced a miscarriage was the subject of "mistreatment and discrimination" in hospital. Another tweeted #Nobodycares aboutthewidow after her husband was killed. The report suggests that it may be possible to use the concerns voiced to provide "counter-narratives" to prevent migration.