Islamic State is using social media and the promise of adventure to lure British Muslim girls to join its cause, an anti-extremism think tank said yesterday, as police attempt to trace three London schoolgirls believed to be heading to Syria.

The three friends, two aged 15 and one 16, left their east London homes last week and caught a Turkish Airlines flight to Istanbul without telling their families.

The Quilliam Foundation said there had been a concerted effort from Islamic State to use websites like Twitter, Ask.fm and Facebook to groom young girls into believing they have a moral duty and obligation to join the militant group.

For girls from conservative Muslim families in Britain, who may be denied the same opportunities as their brothers and male peers, messages offering the chance to “do something with your life” can prove tempting, said managing director Haras Rafiq.

Reject Western values – you’ll never get what you want there

“Many of these girls are not allowed out, or to do certain things in society,” Rafiq said.

“When they are online, they are being targeted with messages of empowerment... ‘Come and do your bit... Reject Western values – you’ll never get what you want there’”.

Islamic State, the militant Sunni Muslim group, declared an Islamic caliphate across parts of Syria and Iraq last summer. It has killed thousands in what the UN has called a reign of terror. The Quilliam Foundation estimates some 600 people from Britain, around 10 per cent of them female, have travelled to Syria and Iraq to join the conflict, mostly with Islamic State.