Heraldo de Madrid - Diplomats, schools in Saudi take safety measures after blasts heard: sources to AFP

The explosions heard in Riyadh came hours after the Houthis in Yemen, which borders Saudi Arabia, claimed their latest attack on the kingdom.

The Iran-backed fighters have launched a wave of attacks on Saudi Arabia since they began a major offensive in Yemen against the internationally-recognised, Saudi-backed government there.

Saudi Arabia and Yemeni government forces have struggled to contain the Houthis' advance, despite a counter-offensive aimed at recapturing territory including the area around a waterway that is crucial to global energy flows.

In Riyadh, home to a large number of non-Saudis, diplomats were instructed to shelter in place in their respective embassies, diplomats told AFP.

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

The measures came after repeated blasts were heard in the city, one of the loudest disturbances there since the start of the Middle East war that began with US-Israeli strikes on Iran in late February.

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

- 200,000 people displaced -

While the Yemen war predates the Iran war, it had come to a near-standstill in recent years, until last month the Houthis launched a lightning offensive against government forces.

They seized large swathes of territory including the area around the Bab al-Mandab strait, a key waterway for global shipping and, crucially, Saudi oil exports.

The fighting in Yemen has in recent weeks become the most active front of the wider regional conflict, which for months has seen violence repeatedly shift focus across the beleaguered Middle East.

In Yemen, one of the world's poorest countries, it is ordinary civilians paying the price, with more than 200,000 people displaced since July, according to UN data.

After declaring a counter-offensive against the Houthis, Yemen's government claimed to have pushed the fighters out of strategic areas on the Red Sea 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.

In Saudi Arabia, the latest blasts came a day after the Houthis claimed attacks on two international airports, while repeating a warning to airlines to avoid Saudi airspace.

"On Tuesday and Wednesday... Abha International Airport and King Khalid International Airport were subjected to attacks targeting their facilities," Saudi Arabia's civil aviation authority said.

An Egyptian and an Algerian national were killed at Abha airport, while a Sudanese national was killed at Riyadh airport, the agency said.

The attacks wounded 36 people, it added.

In a subsequent statement, the Saudi-led coalition fighting the Houthis blamed them for the strikes and vowed a response.

"The brutal attacks by the Terrorist Houthi Militia on civilian and civilian objects in the Kingdom, most recently targeting (the two airports) will not go unpunished," it wrote on X.

- 'Terrified' -

On Wednesday in Yemen, clashes left at least 62 combatants dead, including 37 Houthis, military sources from both camps told AFP.

Saba also reported that a Houthi missile wounded five civilians in Taiz, a city held by government forces.

"We went out into the street to check on the wounded and saw young civilians who had been hit," resident Al-Fateh al-Eisaei told AFP.

"The Houthi shell landed in the middle of the street, right in an area crowded with civilians."

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

Mohammed, a 33-year-old charity worker who fled from Mocha to the city of Aden, told AFP that "people there are terrified" of the Houthis.

F.Cabrera--HdM