A new attack targeted Riyadh's international airport on Sunday, causing a fire, the Saudi-led coalition in Yemen said, a day after a strike killed 12 people and wounded more than 300 in the deadliest such attack on Saudi Arabia in more than a decade.

The coalition said Saudi air defenses had intercepted a cruise missile near King Khalid International Airport. It described Sunday's attack as involving an unidentified projectile that targeted Terminal 4, but provided no further details.

The airport remained closed on Sunday following Saturday's deadly strike, as Iran-backed Houthi forces renewed warnings against using Saudi airports and airspace amid an escalating conflict between the group and Saudi Arabia.

U.S. Secretary of State Marco Rubio condemned the airport attacks, saying they demonstrated a "blatant disregard for innocent civilian life." U.N. Secretary-General Antonio Guterres also condemned Saturday's strike, stressing that attacks on civilians and civilian infrastructure violate international law and must cease immediately.

Despite the airport's closure, Saudi authorities said major international energy events scheduled in Riyadh would proceed as planned.

Houthis warn of further attacks

Earlier on Sunday, the Houthis warned airlines, aviation workers and travelers against using Saudi airports and airspace, describing them as vulnerable to attack and a theater of military operations. The group exempted airports in the holy cities of Mecca and Medina.

"We urge everyone to take our warnings seriously, and Saudi Arabia bears responsibility for any failed interceptions," the Houthis said in a statement posted on X.

The Houthi-run foreign ministry later warned that further Saudi military action in Yemen would trigger a stronger response, saying its actions would be guided by the principle of reciprocity.

"Unless the Saudi enemy stops its aggression and interference in Yemen, worse is yet to come, God willing," the ministry said in statements carried by Houthi-run Al Masirah television.

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

President Donald Trump said on Saturday that the United States was considering joining Saudi strikes against the Houthis, in a conflict that has become intertwined with the wider war on Iran launched by the United States and Israel in February.

Yemen war escalates after ceasefire collapse

The latest attacks mark a sharp escalation in a conflict that has devastated Yemen for more than a decade.

Saudi Arabia entered the Yemen war in 2015 at the head of an Arab coalition seeking to drive the Houthis from the capital, Sanaa. The conflict descended into a prolonged stalemate, with fighting and famine killing hundreds of thousands of Yemenis.

A ceasefire reached between Saudi Arabia and the Houthis in 2022 unraveled this summer, culminating in a rapid Houthi advance that wrested control of the strategic Bab el-Mandeb chokepoint along the Red Sea from Saudi-backed government forces.

The Yemeni government, backed by Saudi Arabia, launched a counteroffensive this week to retake the territory, but its forces have made only limited gains. Meanwhile, the Houthis have placed Taiz, Yemen's third-largest city, under siege.

Saudi Arabia and the Yemeni government have reported hundreds of strikes against targets in Houthi-controlled territory. The Houthis have said the attacks killed civilians, including women and children. Reuters could not independently verify those claims.

The Houthis have not claimed responsibility for Saturday's airport attack, although they have repeatedly warned international airlines against operating through Saudi airspace and said they had shut down Riyadh's international airport.

Airport remains closed as conferences proceed

Saturday's strike, the third attack on Riyadh's airport in a week, killed 12 people, including four Saudis, two Bangladeshis and nationals of the United States, Jordan, Palestine, Syria, Sudan and Egypt, according to Saudi authorities. Officials reported 309 people wounded.

The two earlier attacks on the airport killed four people and caused heavy damage to a Saudi commercial aircraft parked on the tarmac.

On Saturday, all flights were diverted from Riyadh and operations at the airport, which serves a city of about 8 million people, were suspended, according to the Saudi civil aviation authority.

An eyewitness reported seeing an explosion followed by multiple injured people lying on the airport floor. More than a dozen ambulances rushed to the facility, while a video verified by Reuters showed emergency vehicles at the scene.

An injured traveler told Reuters they had seen something fly across the sky outside the airport before part of the ceiling near a departure gate collapsed.

The U.S. Embassy in Riyadh strongly advised American citizens to avoid the airport and surrounding areas.

The continuing attacks have raised concerns over aviation safety as Riyadh prepares to host major international energy and investment gatherings.

A five-day WPC Energy Congress is scheduled to take place at a convention center about 10 kilometers (6 miles) from the airport. Saudi state television said more than 70 ministers, 300 company executives and representatives from over 25 international energy organizations had confirmed their attendance. It was not immediately clear whether participants would attend in person or virtually.

A ministerial meeting of the International Energy Forum was also due to proceed on Sunday, with its plenary session scheduled to take place behind closed doors, according to a media advisory.

Separately, Saudi authorities notified parents that in-person classes would be suspended and replaced by remote learning from Sunday through Thursday for students, teachers and administrative staff.

The latest attack came as Saudi Arabia faces mounting security challenges from the escalating conflict in Yemen, while the continued closure of Riyadh's airport threatens to disrupt travel and major international events.