A British woman, who was a member of a rock band, is believed to be leading Islamic State (IS) jihadis in Syria, investigators said.

In a new video footage, Sally Jones, 45-year-old convert to Islam, is seen urging members of the al-Khanssaa Brigadem, the all-women group set up by the IS, Mirror online reported.

Jones fled to Syria to join the IS and claimed that she wants to behead Christians with a blunt knife.

Jones is wanted in Britain for numerous terror offences. She now calls herself Sakinah Hussain and claims she became a militant after “terrorist nations” Britain and the US invaded Iraq and killed Muslims.

In 2013, she left for Syria with her 10-year-old son Jojo, whom she now calls Hamza. There she wedded computer hacker Junaid Hussain, 20, who was previously jailed for stealing former prime minister Tony Blair’s personal details.

Photographs have previously emerged of the mother-of-two from Chatham, Kent, hiding her hair under a burka, brandishing an AK-47 and pointing a handgun while dressed as a nun.

“This could be the first real evidence that Sally Jones is involved at a high level with al-Khanssaa,” a security official said regarding the video footage.

“Her public statements cause great concern and are being taken incredibly seriously.”

The couple are believed to live in Syria’s Raqqa city where beheadings and crucifixions are routinely carried out in public.