The US secretary of state described it as 'an act of war'. Saudi Arabia insists it was unquestionably 'sponsored' by Iran.
The Yemeni rebels who say they carried out this weekend's attacks on Saudi oil refineries are threatening more strikes against dozens of targets.
Tehran has again denied any involvement even as the debris of drones and cruise missiles were displayed by officials in the Kingdom.
Sky's Middle East correspondent Mark Stone is in Riyadh and sent this report.