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By Rohit Kachroo

LONDON — One of the three British teenagers who left the British capital to live under ISIS is believed to have been killed by an airstrike in Syria, according to her family.

NBC News' U.K. partner ITV News reported that relatives were informed that Kadiza Sultana's home in the militant group's stronghold city of Raqqa was bombed earlier this year.

Kadiza SultanaMetropolitan Police / via EPA

The 17-year-old moved to Syria with two friends from the Bethnal Green area of east London last year.

She traveled with Amira Abase and Shamima Begum, who were aged just 15 when they fled the country to marry fighters. Both are believed to still be living in Raqqa, according to Tasnime Akunjee, a lawyer who was working with Sultana's family.

The three families made international headlines in February 2015 with a series of desperate public appeals for information on the missing teenagers.

Citing her family, ITV News reported that Sultana had become disillusioned with life under ISIS and had been making plans to return to Britain.

Related: Who Is to Blame When Teens Run Away to Join ISIS?

But before she could leave, relatives were informed of the teen's death by other people living in Raqqa.

"We were expecting this in a way," Sultana's sister Halima told ITV News. "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 trio flew from London to Turkey and caught a bus to the border before being smuggled into Syria.

Surveillance images released by London's Metropolitan Police show British teenagers Kadiza Sultana (left), Amira Abase (center) and Shamima Begum (right) passing through security barriers at Gatwick Airport on February 17, 2015.Metropolitan Police Service / AFP - Getty Images

Sultana’s family believes all three girls wed foreigners who were fighting for ISIS. Sultana's husband was an American national of Somali origin who died late last year, her family told ITV News.

Akunjee, the lawyer, told ITV News that Sultana informed her family last summer that she wanted to return home.

He added: "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 ... Leaving ISIS is like trying to escape from Alcatraz, with a shoot-to-kill order added in. It's devastating for the family that it ended like this."

The girls were among more than 800 Britons believed to have left the U.K. to join ISIS or other militant groups in Syria and Iraq, according to U.K. officials.

A surveillance camera image released by London's Metropolitan Police shows British teenagers Amira Abase (left), Kadiza Sultana (center) and Shamima Begum (right) walking with luggage at Gatwick Airport on February 17, 2015.Metropolitan Police Service / AFP - Getty Images

At least 350 have since returned, officials estimate. Some have faced prosecution on arrival in Britain, with others allowed to re-enter society under the watch of security services.

Metropolitan Police Commissioner Sir Bernard Hogan Howe told lawmakers last year the three teens were unlikely to be prosecuted if they returned to Britain unless there was evidence they had committed any specific crimes while with ISIS.

ITV News reported there was no suggestion that either Abase or Begum had given any hint of disillusionment with ISIS.