Seventy-two hours before the attacks in Paris began, messages including images of weapons and the Eiffel Tower began to appear on social media.
Fox News reports four credible social media accounts linked to ISIS shared the content, which also included blessings for the attackers.
The messages translate to "God bless you in your mission" and "support the deployment".
There is also a reference to "our sister", which may suggest that an operative or member of the support group is a woman.
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ISIS has claimed responsibility for the massacre in which 129 were killed and hundreds more injured by a coordinated attack of bombs and shootings.