Riyadh (Saudi Arabia) (AFP) - The Saudi civil defence agency said a kindergarten and a medical complex in Riyadh were damaged by debris from a missile interception on Thursday, as Yemen’s Houthis announced a series of attacks targeting the capital’s airport.

One source briefed on the matter said at least one plane had suffered catastrophic damage at the transit hub, while a second said three aircraft were hit.

Saudi Arabia leads a pro-government coalition fighting against the Houthis in Yemen’s civil war, and the Iran-backed group has repeatedly targeted Riyadh since the conflict roared back to life in July, vowing to hit critical infrastructure and disrupt Saudi airspace.

The scale and frequency of the attacks on the Saudi capital have been unprecedented in the eight months of wider war in the Middle East.

The Houthis announced three separate attacks on Thursday against Riyadh’s airport, which has been increasingly targeted of late. Houthi military spokesman Yahya Saree said the group had also launched missiles at an airport in Najran and an airbase in Khamis Mushait.

Recent attacks have also targeted oil infrastructure in the world’s largest crude exporter.

On Thursday the Houthis warned workers to evacuate Saudi Arabia’s oil facilities, having days before hit a major refinery south of the capital.

Earlier in the day, the Saudi-led coalition fighting the Houthis said it had intercepted two missiles fired towards Riyadh.

Shortly after, the kingdom’s civil defence agency said “interception debris” had damaged a kindergarten and a medical complex in the city. It did not say if there were any casualties or provide details of the damage.

Admissions by Saudi authorities of civilian targets being hit are relatively rare, with officials issuing few statements on Houthi attacks in recent weeks.

- Shelter in place -

After resuming their fight against Yemen’s internationally recognised government following a four-year lull, the Houthis last month seized all of the country’s Red Sea coast in a lightning offensive.

The group, whose heartlands are among the Zaidi Shia Muslims in the northwest, had already controlled the capital Sanaa and most of Yemen’s major population centres since the start of the war in 2014. Riyadh’s military coalition intervened to support the government the following year.

Saudi Arabia and Yemeni government forces have struggled to roll back the Houthis’ latest advance, despite an ambitious counter-offensive aimed at recapturing territory, including the area around a crucial sea route for global energy flows.

In Riyadh diplomats were instructed to shelter in place in their respective embassies, some of them told AFP, after explosions echoed around the city on Thursday morning.

There were no text alerts warning residents, as there had been in the past.

A campaign by the interior ministry has repeatedly warned residents against sharing unauthorised information, images or footage of missiles, drones and their impacts, warning that violators could face legal consequences.

Several residents told AFP that international schools were also taking precautions, with at least one facility sending children into a basement for safety.

“My daughter called me,” one parent told AFP on condition of anonymity, saying she was “completely distraught”.

Two people working in Riyadh’s business hub, the King Abdullah Financial District, told AFP that some companies were evacuating staff from the area.

- ‘Heightened vigilance’ -

Numerous flights at Riyadh’s King Khalid International Airport were delayed or cancelled, according to information posted on signage at the facility.

The airport was yet to acknowledge any disruption, pointing only in a short statement to the “necessity” of contacting airlines before travelling.

The United States urged its citizens in Saudi Arabia to “exercise heightened vigilance” following the attacks targeting the airport, which US government employees now need “special authorisation” to use.

Previous attacks killed a Sudanese national at Riyadh airport, as well as an Egyptian and an Algerian national at Abha airport, civil aviation authorities said on Wednesday.

In Yemen, one of the world’s poorest countries, ordinary civilians are paying the price for the renewed fighting, with more than 200,000 people displaced since July, according to UN data.

The humanitarian crisis caused by the war has left most of the nation’s population dependent on aid.

After declaring its counter-offensive against the Houthis, Yemen’s government claimed to have pushed the fighters out of strategic areas on the Red Sea coast and the port city of Mocha.

But the Houthis insist they are holding their territory, and military sources from both sides contacted by AFP have not reported any major changes on the ground.

Claims by the warring parties have been impossible to independently verify, with the situation moving fast and access for journalists difficult.

The Houthis recently seized areas south of Taiz, the third largest city in Yemen, cutting it off from the government’s temporary capital in Aden and sparking shortages and soaring prices.

“There is a crisis in everything: water, gas, vegetables, everything essential”, said local mother Um Rian.