Tensions are escalating between Saudi Arabia and Iran following a missile attack on the Saudi capital Riyadh.
Saudi air defences intercepted the ballistic missile in the skies over the city in an incident that is jangling nerves across the region.
The attack comes the week after the Trump administration presented evidence it says shows Iran supplied another missile launched at Riyadh's international airport last month.
And it comes as a video has gone viral, apparently made in Saudi Arabia, which visualises open conflict between the two sides.
So what is going on?
Saudi Arabia and Iran back opposing sides in neighbouring Yemen's nasty civil war.
Saudi-led coalition air strikes aimed at shoring up the country's government have killed thousands of civilians and failed to dislodge a rebellion by Iranian-backed Houthis.
Houthis say they launched this missile in retaliation against that air campaign. They are thought to have a stockpile of older scud-style missiles.
But these two recent attacks have been surprisingly accurate and effective, reinforcing claims Iran is more directly involved.
Iran denies allegations it is supplying missiles to the Houthis. What is more likely is the involvement of Hezbollah. READ MORE
