Washington - The French government said it had frozen the assets of two senior Iranian officials.
The event was being held by the armed opposition group the People's Mujahedin of Iran (MEK), which Teheran considers a terrorist group but which Western powers have removed from its blacklists.
Iran immediately denied any involvement, as it did in July when the MEK accused it of being responsible.
The incident comes after President Donald Trump pulled out of an international agreement on curbing Iran's nuclear program, defying allies including France which says that the deal is working.
The Trump administration has vowed to curtail Iranian influence and criticised the Europeans for seeking to evade impending US sanctions on transactions with Iran.
The US considers Iran to be the world's biggest state sponsor of terrorism because of its links with a host of armed groups, particularly the powerful Hezbollah militia in Lebanon and Hamas in the Palestinian territories, as well as other networks in Iraq and Yemen.