Why are Saudi defences struggling to rebuff Houthi attacks?

Saudi Arabia has limited military-industrial capacity and has therefore spent heavily on imported cutting-edge weaponry. (EPA Images pic) RIYADH: Saudi Arabia has poured vast sums into advanced weaponry, yet recent deadly strikes, particularly at Riyadh airport, have exposed shortcomings in its ability to fend off relentless Houthi attacks.

The deadliest attack in Saudi Arabia in more than a decade struck Riyadh airport on Saturday, killing 12 people and wounding more than 300, forcing diplomatic missions to warn their citizens to avoid the facility.

The repeated missile and drone strikes have also damaged the oil-rich kingdom's reputation for stability.

Is Saudi unable to impede attacks?

The repeated Houthi attacks are stretching Saudi air defences and likely depleting interceptors, which reports suggest have been in short supply worldwide.

Saudis have been able to intercept attacks across the country, but several strikes, including ones targeting oil facilities and those against Riyadh's airport, have snuck through.

King Khalid International Airport is one of the world's largest by land area, covering an area of 225 square kilometres about 35 kilometres from the city centre.

Andreas Krieg from the London-based MENA Analytica risk firm said that "even a layered system combining Patriot, THAAD, fighter aircraft and other sensors cannot create an impermeable dome over a country the size of Saudi Arabia", which spans around 2.2 million square kilometres.

They have "to defend Riyadh, airports, oil facilities, military bases, the holy cities and a vast amount of critical infrastructure continuously", he added.

Saudi Arabia has limited military-industrial capacity and has therefore spent heavily on imported cutting-edge weaponry.

Historically, it has relied on a large presence of foreign personnel, contractors and trainers to supplement its forces.

Major weapons purchases from Western manufacturers -- including American, British and French companies -- have become a defining feature of Saudi defence policy and a diplomatic strategy to curry favour with allies.

Why are Houthis escalating?

Krieg said that while Saudi defences are intercepting many incoming attacks, "the Houthis do not need to penetrate the system every time" to achieve their goals.

All they need is the occasional hit, and the repeated strikes on Riyadh's airport show that they "retain the ability to generate follow-on attacks at strategic range", he added.

The surge in Houthi attacks comes as the long-running Yemeni civil war -- in which a Saudi-led coalition backs the internationally recognised government against the group -- has reignited in recent months.

Thomas Juneau, security analyst at Ottawa University, said that Houthis want to "rewrite the rules of the game."

With Saudi warplanes attacking Sanaa airport, which is under Houthi control, the Iran-backed group wants "to do to Saudi Arabia what Saudi Arabia does to them", he added.

The Houthi movement, also known as Ansar Allah, has tens of thousands of fighters that are well-trained, tenacious and battle-hardened in Yemen's harsh, mountainous terrain.

Their missiles and drones have for years posed a threat to oil-rich Gulf neighbours, and have recently reached as far as Israel.

By targeting critical Saudi infrastructure, Houthi's message is "that the price of peace keeps on going up", Juneau said, referring to hopes of finally resolving the Yemen war.

"For Saudi Arabia, this is an absolute disaster because Saudi Arabia has been trying to extricate itself from the war in Yemen for several years," he added.

What are Saudis saying?

"The airport matters enormously" because it is central to Saudi Vision 2030, led by Crown Prince Mohammed bin Salman, which aims to make Riyadh a major hub for tourists, multinational companies, and international events, Krieg said.

"The Houthis understand that."

Krieg warned that while disrupting Riyadh's airport may not erode Saudi military power, repeated attacks inflict economic and psychological costs that exceed the physical damage.

Saturday's airport attack was the deadliest in the kingdom since a 2015 suicide bombing.

It also came on the eve of the country's high-profile convention and entertainment season, with the WPC Energy Congress opening in Riyadh on Sunday.

Authorities previously kept citizens occasionally informed through text-message alerts of impending attacks.

But, those warnings have recently stopped, leaving many citizens wary.

On Saturday, worried diplomatic missions complained of not being regularly briefed by Saudi officials.

Several embassies advised their citizens to avoid Riyadh airport hours before Saudi authorities issued their first official statement.