Yemen's Houthis warned airlines, travelers and airport workers to stay away from Saudi airports, a day after an attack on Riyadh's international airport killed 12 people and wounded more than 300 others.

It was the deadliest such attack in the kingdom in more than a decade and comes amid an escalation of fighting between the Houthis and Saudi-backed Yemeni government forces.

The coalition vowed to respond, and on Sunday Houthi media reported that two Saudi strikes had targeted Sanaa governorate in Yemen, which is controlled by the Houthis.

While the Houthis stopped short of claiming the Riyadh airport strike, they threatened new attacks on the kingdom's airports, except for the holy cities of Mecca and Medina, warning passengers not to travel.

Houthis' warning

"We renew our warning to all airlines, experts, employees, workers and travellers against using Saudi airports and airspace, as they are vulnerable to attack and have become a theater of operations for our forces, with the exception of the airports in (the holy cities of) Mecca and Medina," the Houthis said in a post on X.

"We urge everyone to take our warnings seriously, and Saudi Arabia bears responsibility for any failed interceptions."

A spokesman for the Saudi-led coalition fighting the Houthis in Yemen attributed Saturday's attack to the Houthis, calling it a "full-fledged war crime."

A diplomatic source also attributed the strike to a Houthi missile.

A Western diplomat based in Riyadh told journalists that the official number of injured did not appear to give a full picture of the aftermath.

The number also does not seem to include those who sustained minor wounds, the diplomat said.

Flights suspended

Authorities suspended operations at the airport into Sunday, a senior aviation source told journalists, with air traffic monitor Flightradar24 saying the closure was extended until 2100 GMT. 

A second source working in the aviation sector who helps oversee flights to Riyadh confirmed the halt in operations "until further notice."

"The information we have is... that some systems have been damaged – the radar and communications equipment," the source said, adding that runways also needed to be assessed.

One passenger spoke about a strike they witnessed in the airport's domestic terminal.

"I was at gate 403," the witness said. "I saw 401 hit, I saw injured in front of my eyes. Everyone was running."

Chinese, The US, Canadian, German and Spanish embassies in Saudi Arabia warned their citizens to avoid the airport.

A senior Western diplomat told reporters that several embassies were banning their staff from using the airport "over the next week."

Spillover from war on Iran

Saudi Arabia has stepped up its military involvement in Yemen in recent weeks, launching strikes against the Houthis and backing a Yemeni government counteroffensive after the group seized strategic territory along the Red Sea coast last month.

President Donald Trump said the United States was considering joining Saudi strikes on the Houthis in the conflict, a spillover from the wider war on Iran that the US and Israel launched in February.

The United Arab Emirates said it stands in solidarity with Saudi Arabia after the deadly attack on Riyadh's airport, and expressed support for "all measures" to safeguard the kingdom's security.

UK Defense Secretary Wes Streeting condemned the deadly attack as a "dangerous escalation" and "contemptible."

The Saudi-led coalition said that a projectile had also fallen near King Fahd International Airport in Dammam, in the kingdom's Eastern Province. The coalition also reported intercepting a drone in the region on Sunday.

Saturday's attack has forced the temporary closure of King Khalid International Airport but the Saudi energy ministry said a long-planned international energy conference was still going ahead in Riyadh on Sunday.

The five-day WPC Energy Congress is taking place at a convention center some 10 kilometers from the airport. State TV said more than 70 ministers, 300 company executives and representatives of over 25 international energy organizations have confirmed their attendance.

It was not immediately clear whether the participants would attend in person or virtually.

Planned events go ahead

A ministerial meeting of the International Energy Forum is also set to go ahead on Sunday, with its plenary session to be held behind closed doors, according to a media advisory. No further details were immediately available.

Separately, Saudi authorities notified parents that in-person classes would be suspended and shifted to remote learning from Sunday until Thursday for all students, teachers and administrative staff.

In Saturday's attack, the third on Riyadh's airport in a week, the 12 dead included four Saudis, two Bangladeshis and nationals of the United States, Jordan, Palestine, Syria, Sudan and Egypt, Saudi authorities said.

Saudi Arabia's civil aviation authority said airport operations were temporarily suspended pending damage and safety assessments, without specifying when flights would resume.

Two previous attacks on Riyadh's international airport earlier in the week had killed four people and caused heavy damage to a Saudi commercial plane parked on the tarmac.