Egypt's state-sponsored Islamic authority warned women Wednesday against marrying fighters from the ISIS group online, saying such unions would push them into a "circle of terrorism".

Dar al-Ifta, the body that issues rulings on Islamic sharia law, said it made the warning after noticing several ISIS calls on social networks for girls to marry its members "through video conferences".

"Dar al-Ifta warns girls from adhering to these calls that go against sharia," a statement said.

Such actions would push them into "the circle of extremism and terrorism through illegitimate marriages."

The London-based Institute for Strategic Dialogue said in a recent report that women joining the extremist group in Iraq and Syria are expected to marry its fighters, keep house and bear children.

Since December, Egypt has imposed restrictions on male citizens between the ages of 18 and 40 travelling some countries to stop them from joining organisations like the ISIS, which has captured swathes of territory in Iraq and Syria and is now present in Libya.

European nations are also scrambling to halt a surge in young people wanting to travel to Iraq and Syria to fight with the extremists.