Malcolm Turnbull says the Islamic State is not a 'superpower'

Australia and New Zealand say destroying the myths propagated by Islamic State is a necessary part of the fight against the terror group.

"They are not a superpower. They are not supermen," Prime Minister Malcolm Turnbull said at joint press conference with his New Zealand counterpart John Key in Auckland.

"And that's why it is important for us to carry on that battle, not simply on the field ... but also to take them on in the cyber sphere, where they have been especially effective."

Mr Key said combating IS on social media is a key role for Australia and New Zealand, which both have troops in Iraq as part of the US-led Combined Joint Task Force.