Video report by ITV News Security Editor Rohit Kachroo

One of three schoolgirls who left their homes in Bethnal Green to join the so-called Islamic State (IS) is believed to have been killed by an airstrike in Raqqa, ITV News can reveal.

Kadiza Sultana, 17, is thought to have died earlier this year, after her home in the terror group's stronghold city was hit by a bomb believed to have been dropped by a Russian plane.

The schoolgirl had been living in Syria after leaving her home in east London in February 2015 to join IS.

She had travelled with her friends Amira Base and Shamima Begum, who were both just 15 when they fled, and are believed to still be in Raqqa.

The trio became some of Britain's most famous IS recruits and shocked the nation after leaving their A-Level courses and their families to marry fighters in Syria.

However, ITV News can reveal that Kadiza Sultana had become disillusioned with life in the medieval terror state and was making plans to flee back to Britain.

Kadiza's sister Halima spoke about the family's desperate bid to bring her home Credit: ITV News

Her family were communicating with her from their east London flat to discuss how she might leave Raqqa and cross the border into Turkey, where they hoped to be reunited with the former schoolgirl.

But it is believed Kadiza was killed before she could flee after the property she was staying in was obliterated by the airstrike in May.

ITV News can reveal excerpts of interviews given by Kadiza Sultana's sister Halima Khanom during the tense months when the desperate family hoped to secure her return to the UK.

The interviews were filmed by journalist Joshua Baker and include recordings of phone calls between Halima and her younger sister before her death.

In one such phone call, Kadiza expressed her fears, saying: "I don't have a good feeling, like I feel scared."

"If something goes wrong that's it," she added.

In one phone call, Halima speaks to her 'terrified' sister about plans to get her back to the UK. Credit: ITV News

The conversations are especially poignant after ITV News established via contacts in Raqqa the reports about Kadiza’s death.

The reports of her death are unverified and the nature of the Syria conflict means the precise details are impossible to confirm.

But it is believed the teenager was inside a residential building when it was struck by the airstrike.

Her family were informed of Kadiza’s reported death by other people in Raqqa and confirmed details in a statement to ITV News.

Halima said: "We were expecting this in a way. But at least we know she is in a better place.

"We do not wish her name to come up in the headlines again... She is gone and we would like to respect her wishes."

The families of all three Bethnal Green schoolgirls made international headlines in February 2015 after making a series of desperate public appeals for information on the missing teenagers.

Halima and relatives of the two other girls then travelled to Istanbul with ITV News to retrace the steps of the trio, who flew to Turkey and caught a bus to the border before being smuggled into Syria.

ITV News followed relatives of the girls to Turkey as they retraced their journey. Credit: ITV News

It is believed that all three wed fellow foreigners who were fighting for the Islamic State. Kadiza's husband was an American national of Somali origin who died late last year.

All three families were represented at the time of the schoolgirls' disappearance by lawyer Tasnime Akunjee, who was working with the Khadiza's family on a possible escape plan.

He told ITV News the teenager had quickly become disillusioned with Isis and told her family last summer that she wanted to return home.

"You would move heaven and earth to get any child back from a danger zone, and this family had done all they could and stretched every sinew to get their daughter, their sibling back home.

"But there is always the situation when you have a person in a warzone that the worst could happen, and unfortunately it just wasn't possible to have her home before the risk caught up with her."

Mr Akunjee also said there are many examples of people who have gone out to Syria and discovered the situation is very different to how it is described in IS propaganda and want to come back.

It's devastating for the family that it ended like this. Tasnime Akunjee

The Bethnal Green schoolgirls were among more than 800 Britons believed to have left the UK to join IS or other militant groups in Syria and Iraq.

It is thought that around 400 may have since returned. Some have faced prosecution on arrival in Britain, with others allowed to re-enter society under the watch of security services.

Last year, Metropolitan Police Commissioner Sir Bernard Hogan Howe told MPs the Bethnal Green trio would be unlikely to be prosecuted if they returned to Britain, unless there was evidence they had committed any specific crimes while with IS.

Sir Bernard apologised after a letter warning the families of the risk of radicalisation did not reach them.

ITV News has no information about the fate of the other two Bethnal Green schoolgirls.

There is no suggestion that either Amira Abase or Shamima Begum have given any hint of disillusionment with IS. It is believed the pair continue to live in Raqqa.