British IS recruiter Sally-Anne Jones was reportedly killed in a US drone strike in Syria in June.
Jones, from Chatham in Kent, joined so-called Islamic State after converting to Islam and travelling to Syria in 2013.
Her death was first reported by The Sun.
The BBC's security correspondent Frank Gardner said Jones had been a useful propaganda agent for IS on social media and her death would be "significant".
Whitehall officials have declined to comment publicly. However, they have not denied the story, and US sources are confident she was killed in an unmanned drone strike in June, our correspondent added.
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