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 attacks targeting the capital's airport.

Two witnesses said that a plane at the airport belonging to national flag carrier Saudia had cracks and holes in its fuselage. A source briefed on the matter said three planes suffered damage.

Saudi Arabia leads a pro-government coalition fighting the Houthis in Yemen's civil war. 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 attacks on Thursday against Riyadh airport. Houthi military spokesman Yahya Sarea said the group 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.

The Houthis on Thursday 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.

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 casualties or provide details of the damage.

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 in 2015 to support the government.

Saudi Arabia and Yemeni government forces have struggled to roll back the Houthis' 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 at their respective embassies, some of them said, after explosions echoed around the city on Thursday morning.

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

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

Numerous flights at Riyadh's King Khalid International Airport were delayed or cancelled, according to information posted for passengers.

The airport did not immediately 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 at 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, civilians are paying the price for the renewed fighting, with more than 200,000 people displaced since July, according to UN data.

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

After declaring its counter-offensive, Yemen's government claimed to have pushed Houthi 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 have not reported any major changes on the ground. (AFP)



Edited by Cecil Wong