A man wearing a black ski mask and holding an AK-47, seated alongside two others, made the threat in a video bearing the Islamic State's Amaq news agency logo and showing footage of two attacks in Tehran in June claimed by the militant group.

"The same way we are cutting the necks of your dogs in Iraq and Syria we will cut your necks in the center of Tehran," the man said, speaking accented Farsi.

Islamic State, a Sunni Muslim group which has sought to establish a caliphate in parts of the Gulf but is now under pressure from national armies and international groups in Syria and Iraq, sees Iran, which is predominantly Shi'ite, as one of its biggest enemies in the region.