An Australian woman has reportedly left her two young children to join Isis, telling the babysitter she was going to pick up a new car and never returning.

Jasmina Milovanov, 26, is thought to have left her home in Sydney earlier this month and travelled to Syria. She text her ex-husband to tell him that their five and seven-year-old children needed looking after.

Ms Milovanov’s family told Australia’s Ten News that they were concerned she had been brainwashed.

“She is so young and naïve all we can do is pray,” her mother told the station. She added that “she never talked about it, she never mentioned anything.”

Ms Milovanov converted to Islam and now calls herself Assma Abdullah. According to Australia’s Daily Telegraph she is friends online with a notorious jihadi bride recruiter from Melbourne, Zehra Duman.

The paper reported that she texted her ex-husband who was in Turkey at the time to tell him she was in “sham” which is Arabic slang for Syria. She is not believed to speak fluent Arabic, however.

Her ex-husband told reporters he was concerned with her activity online and the pair had spoken about her “extreme” Facebook posts and that she converted to Islam in her late teens.

“She will jump. She is the type of girl that starts dreaming about something and wants to do it,” he said.

A former friend of Ms Milovanov also spoke to the ABC News, saying that she had often spoken about marrying a jihadi fighter.

“What we believe is Assma really wanted to get married, she was very lonely... we think that's how they've encouraged her to go,” the friend said.

“She's not a terrorist. I don't believe she's gone over there to fight,” said the friend, who did not want to be named.

They reportedly lent her $2,500, which her friends subsequently realised must have been to fund her trip.

Australian authorities believe that there are up to 40 Australian women who have travelled to Syria and Iraq to help terrorist fighters, the Mail Online reported.