At least 12 people have been killed and 309 injured in an attack on an airport in the Saudi capital Riyadh, local authorities say.

The deaths included four Saudis, two people from Bangladesh and one person each from the US, Jordan, Palestine, Syria, Sudan and Egypt, the Saudi civil aviation authority said. Operations at King Khalid International Airport have been suspended.

A Saudi-led military coalition later vowed to respond to the attack, which it blamed on Yemen’s Houthis and called a “war crime”.

The Houthis have not taken responsibility for the attacks but the group were behind separate strikes on the airport on Thursday that killed three people and damaged a plane.

Fighting has recently escalated between Yemen’s Saudi-backed government forces and the Houthis, who control most of the country. Saturday’s attack was the deadliest in the kingdom since May 2015.

As well as the strikes on Riyadh’s airport, a projectile also fell near King Fahd International Airport in Dammam in eastern Saudi Arabia on Saturday, the Saudi-led coalition said.

The attacks come a day after authorities said three Saudis including a pilot were killed in two attacks on the airport by the Iran-backed Houthis the day prior. Another three people were killed in Houthi attacks on two Saudi airports on 6 and 7 October.

In Saturday’s statement, the Saudi civil aviation authority said some of the injured were “in critical condition”.

It said damage to the airport was being assessed.

An eyewitness who said they had been in the domestic terminal told the news agency that they had seen gate 401 hit and “injured [people] in front of my eyes”, adding: “Everyone was running.”

More than a dozen ambulances were seen rushing to the airport, according to news agency Reuters, citing an eyewitness.

Saudi-led coalition spokesman Maj Gen Turki al-Maliki later said the attack on one of the passenger terminals resulted in deaths and injuries among civilian passengers and airport staff.

He described the attack as a “full-fledged war crime”.

US Secretary of State Marco Rubio strongly condemned recent attacks on Saudi Arabia as he confirmed an American citizen was killed in the strikes.

When later asked by reporters whether the US planned to join Saudi Arabia in carrying out strikes against the Houthis, President Donald Trump said: “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.”

António Guterres, Secretary General of the United Nations, said he was “deeply shocked” by the attacks which he called a “violation of international law” that “must cease immediately”.

The attacks were also condemned by Egypt, Palestine and Qatar.

Western embassies in Saudi Arabia warned their citizens to stay away from the Riyadh airport. The UK Foreign Office told British nationals to avoid the area “until the airport is secure”.

Several Gulf airlines said they had cancelled their flights to and from the airport, with Kuwait Airways citing the “security situation” there.

All flights to Riyadh have either been diverted or cancelled, aviation tracker Flightradar shows.

The Houthis say they are targeting Saudi Arabia over its support for government forces in Yemen’s civil war.

The conflict worsened after the Houthis seized strategically important stretches of the Red Sea coast in a rapid offensive.

That included the port of Mokha on the Bab al-Mandab Strait, which is the narrowest point of the Red Sea and a chokepoint for global shipping. Yemeni pro-government forces have since said they had “secured” the strait at the southern end of the Red Sea.

The Saudi-led coalition was formed in 2015 after Arab countries joined forces to stop the Houthis taking over Yemen from the country’s internationally recognised government.

A temporary ceasefire was brokered in 2022 after years of air strikes and ground fighting led to the deaths of hundreds of thousands of people, triggering one of the world’s worst humanitarian crises.

But the informal truce began to unravel in July.

The Houthis announced a “maritime embargo” against Saudi Arabia and began missile and drone attacks on Saudi airports, oil facilities and tankers in the Red Sea.

They said they were retaliating against what they described as a years-long Saudi blockade and for an air strike on the airport in Yemen’s capital Sanaa, which is controlled by the Houthis.