"I'm gonna practice my beheading skills": the most disturbing tweets from Jihadi brides.

Free rent, groceries, and marriage to the man of your dreams. This is the kind of propaganda persuading teenage girls to run away — and join the Islamic State.

The Halane sisters fled Britain in 2014 to marry Islamic State fighters in Syria.

The 15-year-old twins, Zahra and Salma Halane, were well-liked at school. They were described by classmates and teachers as intelligent and friendly.

“They were friends with every single person. You would walk around the corridor and they’d smile you or they’d wave,” one former classmate told ABC program Foreign Correspondent. “They were so bright and enthusiastic about every thing.”

But two years ago, the Halane sisters disappeared. Eventually, they were found to have travelled to Syria to be married to Islamic State fighters.

Now, girls are 17. And if their Twitter accounts were anything to go by, they are your average teenage girls — with an added element of fierce extremist dedication.

Related content: The creepy blogs luring Australians into joining ISIS.

As last night’s Foreign Correspondent programme revealed, the Halane sisters and other western teenage girls ‘LOL’ and chat idly about trivial things (take Moroccan oil, for example), but they also revel in the conflict Islamic State perpetrates and the fear it mongers.

“Happy #9/11, happiest day of my life. Hopefully more to come,” one tweet reads.

Another says: “I’m gonna practice my beheading skills on a chicken. It looks fun.”

The girls were dubbed by the press as the “Terror Twins,” a title they reportedly enjoyed.

But these tweets are only part of a powerful online recruiting process based on the glamourisation of life under IS.

They brag about having free rent, free electricity and water, free medical check-ups. They spread the dangerous message: You too can have a house full of appliances (including milkshake machines) — at the price of having to marry an extremist, bloodthirsty soldier.

This is how the Halane twins came to join IS in the first place; they came into contact with a woman identified as Aqsa Mahmood — a young woman from Glasgow, who travelled to Syria several years ago.

She is now regarded as a sort of ‘mother’ to foreign fighters, writing a blog about becoming a jihadi bride.

She “educates” the girls on every aspect of life as the wife of an ISIS soldier. She instructs the young women on how to flee their homelands, what to expect when they call their parents to tell them they’re never coming back, and what life will be like for them.

“Your day will revolve around cooking, cleaning, looking after and sometimes even educating children. And that’s the reality, my dear sisters,” she writes. “We are created to be mothers and wives. As much as the western society is wont to refuse on this, with a hedon feminist mentality.”

She also gives tips to western girls on what is expected of the wives once their husbands die — which they inevitably will.

Indeed, both the husbands of the Halane twins are already dead.

The Halane girls are just two of 550 western women believed to be currently living under Islamic State, including around 30 to 40 Australian women, Foreign Minister Julie Bishop.

It’s scary stuff — and there’s no end in sight.

What do you think should be done to stop young women becoming Jihadi brides?

Read more: 

Julie Bishop on why young Australian women are becoming radicalised.

Western women are being recruited to join militant groups in Iraq and Syria. 

Australian women are fleeing overseas to become Jihadi brides.

British schoolgirls packed their bras and epilators before fleeing to Syria.