CAIRO — The latest attack on the international airport in Saudi Arabia's capital of Riyadh killed 12 people and injured over 300 others, civil aviation authorities said early Sunday, with some in critical condition.

The attack was the deadliest in any Gulf Arab country since the start of the Iran war, whose fronts have expanded to include the recent surge in fighting between the Iran-backed Houthi rebels in Yemen and Saudi-backed government forces there.

The statement, which did not assign blame for the attack, said the dead included four Saudi citizens as well as two Bangladeshi nationals, a Palestinian, a U.S. citizen, an Egyptian, a Jordanian, a Syrian and a Sudanese. It said the injured were being treated at several hospitals.

The attack — the latest of several in the past week on King Khalid International Airport that killed four people — is expected to increase Saudi pressure on allies including the United States to provide military support for the kingdom.

Shortly after the attack on Saturday afternoon, President Donald Trump said he was evaluating whether the U.S. should join Saudi strikes against the Houthis. "We may. We're going to look at it," Trump said. "We just found out about the recent attack. So we'll make a decision. We move very quickly." A missile struck an airport complex housing terminals 3 and 4 for domestic flights, a regional official said, speaking on condition of anonymity because they weren't authorized to speak to the media.

The surge in attacks, including against other Saudi airports, military facilities and oil infrastructure, has come in the week since a Saudi-led coalition launched a major military offensive against the Houthis. There was no immediate statement from the rebels, who earlier Saturday accused Saudi Arabia of striking Sanaa International Airport in the Houthi-held Yemeni capital. The rebels at times take days to claim responsibility.

Riyadh airport operations were suspended Saudi civil aviation authorities earlier said airport operations were suspended. An official notice to aviators said the suspension was through midnight. The airport had a heavy police presence, with all entrances blocked, and lights around the complex were dimmed.

Flights diverted elsewhere, the Flightradar24 tracker said. Countries including the United States, Britain, Germany, Australia and Canada warned citizens to avoid the airport. Statements later turned to condolences.

Later on Saturday, the Saudi-led coalition said a projectile had fallen near King Fahd International Airport in Dammam and a Houthi-launched ballistic missile had been intercepted in Al-Kharj governorate, southeast of Riyadh.

The attacks on Saudi Arabia, the world's top oil exporter, have rattled markets and the region. And yet the Saudi energy ministry hours after the latest one was still promoting a major international energy conference set to begin in Riyadh on Sunday.

Fighting between the Houthis and Saudi-backed Yemeni government forces has escalated, with the Saudi-led coalition providing air support for government forces attempting to reverse recent Houthi gains along Yemen's Red Sea coast. Those gains gave the rebels better surveillance of shipping on a corridor that is a crucial alternative to the Strait of Hormuz, where Iran has been attacking ships.

Though the Houthis have told the AP and others they are only targeting Saudi shipping as part of a blockade in retaliation for one imposed on them, concerns about wider attacks persist. The Houthis previously attacked other ships after the war in Gaza began, calling it solidarity with Palestinians. A U.S. bombing campaign sharply limited that.

Saudi Arabia has run low on interceptors, officials say Saudi Arabia is running low on missile interceptors and has asked France, Britain, Pakistan and Egypt to deploy air defense support to the region, regional officials told the AP last month, with one noting that the U.S. has seen its own stock dwindle during the war with Iran.

Officials have said U.S. assistance has included intelligence sharing, target identification and planning for the latest offensive against the Houthis.

Earlier Saturday, Saudi Arabia said its foreign minister and Omani counterpart spoke by phone about the importance of "supporting diplomatic solutions to de-escalate tensions" in the region. Oman, which lies across the Strait of Hormuz from Iran, has played a mediator role at times in the region.

Flight disruptions are growing The Houthis this week warned global airlines "for the last time" about the potential consequences of operating in Saudi airspace, which they described as a theater for their military operations.

Before the latest attack, Air India, FlyDubai, Lufthansa Group and Pakistan International Airlines were among airlines suspending flights to and from Riyadh and other Saudi airports for varying periods.

The European Union Aviation Safety Agency had expanded its guidance on Saudi airspace, noting the Houthis' ability to strike targets deeper inside the kingdom, including Riyadh, and a "greater focus on aviation infrastructure." The missile and drone attacks and interception efforts "create an increased risk of misidentification of civil aircraft," it said.

Two regional officials said Houthi attacks on the Riyadh airport on Thursday damaged three planes. The officials spoke on condition of anonymity because they weren't authorized to brief the media. The Saudi national carrier said one of its aircraft was damaged while it was on the ground, with no passengers on board.

Meanwhile, Saudi authorities warned the public this week that "filming, publishing or sharing information related to countering missiles and drones and their impact sites exposes you to legal liability." Anna reported from Jerusalem.