CAIRO (AFP) - Egypt's state-sponsored Islamic authority warned women on Wednesday against marrying fighters from the Islamic State in Iraq and Syria (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 militants "through video conferences".

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

Such actions would push them into "the circle of extremism and terrorism through illegitimate marriages that neither please Allah nor his Prophet."

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 to Turkey and Libya to stop them from joining organisations like the Islamic State, which has captured swathes of territory in Iraq and Syria and is now present in Libya.

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

And Egypt is fighting an Islamist insurgency spearheaded by an ISIS affiliate, Ansar Beit al-Maqdis, in North Sinai province that borders Israel and the Gaza Strip.