Saudi Arabia retaliated with heavy air strikes on Sanaa, the rebel-held capital of Yemen, after intercepting a Houthi-launched missile north-east of Riyadh.
The rebels have fired dozens of missiles into Saudi territory since the conflict began, but the attack on Saturday evening demonstrates that much of the GCC, including the UAE, is within range of the Yemeni-built missile
The Iran-backed Houthis claimed the Burkan 2-H missile, which has a range between 800 and 2,000 kilometres, had struck its target in King Khaled International Airport, 20km north of Riyadh.
However, Colonel Turki Al Maliki, the spokesman for the Saudi-led coalition fighting against the Houthis, said the missile - which was fired from Yemeni territory at 8.07pm local time on Saturday - was intercepted by Saudi forces.
This is the first time a Houthi missile has come so close to a heavily populated area. It also appears to be the farthest that such a missile has ever reached inside Saudi Arabia. Riyadh is about 700km north of the border with Yemen.
The Houthis in recent months have boasted of a new escalation in the conflict, pledging to attack Saudi Arabia and threatening the UAE.
In September, Saudi Arabia intercepted a Houthi-launched missile aimed at one of its largest military bases located in the city of Khamis Mushait, about 100km from the Yemeni border.
The Houthis have also fired missiles to within 70km of Mecca, once last month and another attempt in July.
However, the missile launched on Saturday proved to have the longest range yet, more than 200km than the one aimed at Mecca.
The attack was condemned by leaders both in the region and beyond.
Sheikh Mohammed bin Zayed, Crown Prince of Abu Dhabi and Deputy Supreme Commander of the UAE Armed Forces said the UAE “strongly and resolutely stands with the brotherly Saudi kingdom while confronting all challenges that target its security and the region’s security and stability.”
The UAE Minister of State for Foreign Affairs, Dr Anwar Gargash, dismissed Houthi threats as "stupid".
US President Donald Trump, who is currently on a five-country tour of Asia, suggested that Iran was behind the firing of the missile.
"A shot was taken by Iran, in my opinion, at Saudi Arabia. And our system knocked it down," Mr Trump said, a reference to the Patriot missile batteries that Saudi Arabia purchased from the US.
The Yemeni missile, a Burkan 2-H, is "quite an impressive missile for its size," Ryan Barkenlau, founder of the geostrategic consultancy Strategic Sentinel, said. And though only a handful of the missiles exist, the attacks are likely to continue. "I do not see why they would halt their attacks barring some sort of diplomatic or military intervention on the part of the Saudi government or some other incentive. Even though this missile was shot down, I would still say it succeeded in bringing the situation close to the minds of Saudi citizens and the government with it, coming so close to the busy airport.”
Coalition spokesman Col Al Maliki said the “hostile act” by the Houthis was a result of “the continuous smuggling of arms and missiles” from other groups in the region.
“Their goal is to threaten the security of Saudi Arabia and to target civilians,” he said, noting that the firing of ballistic missiles towards populated cities and villages violates international law.
Sources in Yemen told The National that 17 bombs fell overnight on rebel-held Sanaa, apparently in retaliation for the missile launched at Riyadh. Photographs showed the destruction of Al Sabeen Square, where tens of thousands congregated to celebrate former president and Houthi-allied politician Ali Abdullah Saleh in August.
In Saudi Arabia, meanwhile, people posted photos and videos on social media showing the Houthi missile being intercepted by four US-built Patriots.
The Saudi-led coalition, which includes the UAE, has been fighting alongside the forces of the internationally-recognised government of President Abdrabu Mansur Hadi against the Houthis since March 2015. They have driven the Houthis from much of southern Yemen but the fighting has become bogged down in Taez province and along the Red Sea coast.
For decades, Riyadh backed former president Ali Abdullah Saleh, who ruled Yemen from its unification in 1990 until he resigned under pressure in 2012, ceding power to his vice president Mr Hadi.
But in 2014, Mr Saleh aligned himself with the Houthis, against whom he had fought six wars when he was president. The two now jointly control Yemen's northern highlands and the capital Sanaa.
Compounded by poverty, cholera and looming mass starvation, the war in Yemen has claimed more than 8,500 lives.