Bethnal Green schoolgirl who joined Isis believed to have been killed in an air strike

A schoolgirl from Bethnal Green who travelled with two other teenagers to join the Islamic State (Isis) in Syria is believed to have been killed by a Russian airstrike. A-Level student Kadiza Sultana, 17, is believed to have left her home in east London during the Easter holidays in 2015 to join the extremists.

The Bethnal Green Academy student was joined by her friends, Amira Abase and Shamima Begum, both 15-years-old when they all travelled to Raqqa, Syria. The trio then married foreign IS (Daesh) fighters in the terror group's de facto capital.

Sultana is believed to have died earlier this year when the residential home she was staying in was hit by a bomb believed to have been dropped by a Russian plane. The other two girls are still believed to be living in Raqqa.

ITV News spoke to Sultana's sister, Halima Khanom, who said her sibling had become disillusioned with life in the caliphate and planned to return to the UK.

Her death has not been independently verified by IBTimes UK or UK authorities and the secretive nature of the city means details are often impossible to confirm. However, Sultana's death was reported to her family by other people inside Raqqa.

Halima said to ITV: "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."

Her family travelled to Istanbul to trace the steps of the schoolgirls after making desperate public appeals for information on the missing teenagers.

Sultana's husband in Syria was an American national of Somali origin but despite getting married, Sultana wanted to return home. In one phone call recorded by ITV shortly before her death, she said: "I don't have a good feeling, like I feel scared. If something goes wrong that's it," she said according to the broadcaster.

Tasnime Akunjee, the solicitor for the family told The Guardian: "The family are devastated. A number of sources have said that she has been killed and she has not been in contact with the family for several weeks. Over a year ago, she had been talking about leaving. There was a plan to get her out." The British Foreign Office could not confirm reports of her death, according to the newspaper.

Akunjee told ITV: "Leaving Isis is like trying to escape fro Alcatraz, with a shoot-to-kill order added in ... Perhaps the only benefit out of this is as a tombstone and a testimony for others of the risks of actually going to a war zone, to dissuade people from ever making that choice."

An estimated 800 Britons are believed to have left the UK to join IS or other militant groups fighting in Syria and Iraq. Around 400 are estimated to have returned.