Several loud explosions were heard in the Saudi capital Riyadh on Wednesday, according to a Reuters witness on the ground - as some residents received mobile phone alerts warning of a hostile aerial threat for the first time.
The alerts, unprecedented in their nature, signal a significant escalation in Iran's retaliatory campaign against Gulf states following the US-Israeli offensive launched on February 28.
Saudi Arabia - despite its official non-involvement in the conflict - has been increasingly drawn into the line of fire as Tehran systematically targets the infrastructure, energy assets and now potentially the capitals of Washington's Gulf allies.
Riyadh, home to millions of residents and the seat of the Saudi government, has never previously issued civilian aerial threat warnings of this kind, making Wednesday's alerts a historic and deeply unsettling moment for the Kingdom.
The source of the explosions and the nature of the aerial threat were not immediately confirmed by Saudi authorities.