RIYADH — At least 12 people were killed and 309 wounded in a strike on Riyadh's King Khalid International Airport on Saturday, the deadliest attack on Saudi Arabia in more than a decade, as the Iran-backed Houthis press an escalating campaign they launched this summer.

The Saudi civil aviation authority said the dead from the third attack on the airport this week included four Saudis, two people from Bangladesh, and one person each from the United States, Jordan, Palestine, Syria, Sudan and Egypt. Officials put the number of wounded at 309 in the latest count.

Hospitals were flooded with casualties brought by ambulance and helicopter, some in critical condition, after the attack, which came without warning.

US President Donald J. Trump said Washington was weighing whether to join Saudi strikes on the Houthis in the conflict, a spillover from the war on Iran that the United States Israel launched in February.

Conflict Escalates After Yemen Ceasefire Unravels

The two previous attacks on the airport this week killed four people and heavily damaged a Saudi commercial aircraft parked on the tarmac. The strikes have exposed vulnerabilities in Saudi defense capabilities as the kingdom wages an air campaign against the Houthis in support of a ground war by the Yemeni government against the Iran-backed group.

The Houthis have not claimed responsibility for Saturday's strike, but the Saudi-led military coalition vowed to respond.

Asked whether the United States planned to join Saudi strikes on the Houthis, Trump told reporters: "We may. We're going to look at it. We just found out about the recent attack, so we'll make a decision. We move very quickly."

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

Saudi Arabia and the Yemeni government have claimed hundreds of strikes on targets in Houthi-held territory, while the Houthis have said those strikes killed civilians, including women and children. Reuters could not independently verify those claims.

The Saudis entered the Yemen war in 2015 at the head of an Arab coalition seeking to drive the Houthis from the capital, Sanaa. The conflict became a bloody stalemate in which hundreds of thousands of Yemenis were killed by fighting and famine.

A 2022 ceasefire between the Saudis and the Houthis unraveled this summer, culminating in a lightning Houthi advance that seized the Red Sea choke point of Bab el-Mandeb — the strait linking the Red Sea to the Gulf of Aden and a critical passage for commercial shipping between Asia and Europe — from Saudi-backed government forces. The Saudi-backed Yemeni government launched an offensive this week to try to retake that territory but has made only slow gains, even as the Houthis placed Taiz, the country's third-largest city, under siege.

Airport Shut, Airspace Declared a Military Zone

All flights were diverted from Riyadh on Saturday and operations at the airport, the capital's main international gateway serving a city of 8 million people, were suspended, the civil aviation authority said. The head of the Houthi media office posted on X that the group had "shut down Riyadh international airport."

The Houthis have warned international airlines against operating flights through Saudi airspace, saying it has become a theater of their military operations, with the exception of airspace over the holy cities of Mecca and Medina. Saudi airspace sits along major corridors linking European and Asian destinations, giving the warnings significance beyond carriers serving Riyadh directly.

An eyewitness at the airport described seeing an explosion and then multiple people lying injured on the ground inside. More than a dozen ambulances were seen rushing toward the facility, and a video verified by Reuters showed ambulances at the airport. An injured traveler told Reuters they saw something fly across the sky outside the airport before part of the ceiling near a departure gate collapsed.

The US Embassy in Riyadh said it "strongly recommends all US citizens avoid this airport and surrounding areas."

Earlier Houthi attacks had already prompted a number of carriers to suspend or cancel services to the Saudi capital, shortly before Riyadh is due to host major energy and investment conferences. Organizers of those events said ahead of Saturday's strikes that they would go ahead as planned.

Attention now turns to whether the United States joins the Saudi campaign, when airport operations can resume, and whether Riyadh's scheduled conferences proceed as organizers have pledged.

— Reuters