Three British schoolgirls, two of them of Bangladeshi origin, have fled the UK in a suspected bid to join Islamic State militants after contacting a female British member of the terror group who travelled to Syria to marry a jihadist.

Shamima Begum, 15, Kadiza Sultana, 16, and an unnamed 15-year-old, all from east London, flew to Istanbul in Turkey from Gatwick airport on Tuesday without leaving any messages behind for family or friends.

Shamima is possibly travelling under the name of Aklima Begum, UK police said. The third girl is not being named at the request of her family.

Both the named girls are British-born Bangladeshis, speak English with London accents and also speak Bengali.

Scotland Yard detectives yesterday appealed for any information about the missing girls, who all go to the Bethnal Green Academy school and were described as 'three normal schoolgirls' and 'straight-A students'.

Just two days before their disappearance, Shamima is understood to have been in contact with a female British ISIS member who now advises those desperate to join the terror group.

On Sunday, a Twitter account appearing to belong to Shamima tweeted to an account associated with female ISIS member Umm Layth, formerly known as Aqsa Mahmood.

She wrote: '@Muhajirah_ follow me so i can dm you back'. 'DM' refers to a direct message, which allows users of the social network to communicate privately with each other.

Privately-educated Mahmood, 20, left her privileged life in Glasgow to marry an ISIS fighter in Syria in November 2013.

All three girls left their homes at 8:00 am on Tuesday morning and met at Gatwick Airport, where they boarded a Turkish Airlines flight to Istanbul.

Counter Terrorism Command (SO15) Commander Richard Walton said: “We are extremely concerned for the safety of these young girls and would urge anyone with information to come forward and speak to police. Our priority is the safe return of these girls to their families.

"We are reaching out to the girls using the Turkish media and social media in the hope that Shamima, Kadiza and their friend hear our messages, hear our concerns for their safety and have the courage to return now, back to their families who are so worried about them."

Shamina is described as 5''7" tall, and wearing black thick rimmed glasses, a black hijab, light brown and black leopard print scarf, dark red jumper, black trousers and jacket.

Kadiza is described as 5'6" tall, of slim build and wearing black rimmed glasses, a long black jacket with a hood, grey striped scarf, grey jumper, dark red trousers, carrying a black holdall.

The third missing girl is described as 5'6" tall, of slim build, wearing black thick rimmed glasses, black head scarf, long dark green jacket with fur lined hood, light yellow long sleeved top, black trousers, white trainers carrying a black Nike holdall.

ISIS supporters are believed to be offering cash incentives to encourage schoolgirls to travel to the group's de facto capital Raqqa and marry fighters.

It was reported in December that ISIS channels money for travel expenses through international money wire systems, enabling the group's UK cell to offer significant sums of cash to disenfranchised teenagers.