A group of mothers whose children have joined the extremist Islamic State of Iraq and Syria (ISIS) group is reaching out online to persuade their sons and daughters to return home.

In an open letter posted to social media websites Wednesday, the group Mothers for Life says young men and women who have travelled to Syria and Iraq should remember that Islam requires them to honour their parents and spare them suffering.

The mothers, who come from seven countries including Canada, France and the United States, also want to help other families struggling to bring their children home.

Calgary mother Chris Boudreau, whose son, Damian Clairmont, was killed in Syria last year, says the idea is to "fight fire with fire" because ISIS has been using social media to lure vulnerable youngsters away from their families.