Iran said Monday that the missile-and-drone attack on major Saudi oil sites was an act of ``legitimate defense'' by Yemen's Iran-allied Houthi rebels. The Sept. 14 assault was claimed by the Houthis, though Saudi Arabia says it was ``unquestionably sponsored by Iran.'' The kingdom has been at war with the Houthis in Yemen since March 2015. Iran denies being responsible and has warned any retaliatory attack targeting it will result in an ``all-out war.'' Iran's Foreign Ministry spokesman Abbas Mousavi on Monday called Saudi accusations ``baseless,'' adding that Iran supports the Houthis though ``spiritual and political'' means. He added that ``cease-fire and dialogue'' was the only face-saving solution for Saudi Arabia. Cabinet spokesman Ali Rabiei said the world has ignored another possibility, that the Houthis could have used Russian weapons seized from the Yemeni army or that they had procured them on the weapons market. Saudi Crown Prince Mohammed bin Salman told ``60 Minutes'' in an interview that aired on Sunday that ``only a fool would attack'' major Saudi oil sites and urged ``strong and firm action to deter Iran.'' The attack on oil facilities has heightened tensions between Tehran and Washington. US-Iranian relations have deteriorated since President Donald Trump last year pulled America out of the 2015 nuclear deal between Iran and world powers and re-imposed sanctions that sent the country's economy into freefall. Iran's Foreign Minister Mohammad Javad Zarif criticized Europe for failing to save the nuclear deal from unraveling. * This story was edited by Ahram Online.