An attack on Riyadh's main airport on Saturday killed 12 people and injured 309 others, Saudi Arabia's civil aviation authority said. Some of the injured were in critical condition.

It was the deadliest attack on any Gulf Arab country since the Iran war began in February, the Associated Press reported. Several earlier attacks on King Khalid International Airport in the past week had killed four people. The airport suspended flights after Saturday's strike.

The dead included four Saudi citizens, two Bangladeshis and one person each from the United States, Egypt, Jordan, Syria, Sudan and the Palestinian territories, officials said. Their statement did not say who carried out the attack. The Washington Examiner reported that missiles hit two domestic flight terminals.

Secretary of State Marco Rubio blamed Yemen's Iran-backed Houthi rebels. "These reprehensible attacks demonstrate a blatant disregard for innocent civilian life. They must stop now," he said. He confirmed an American citizen was among the dead.

President Donald Trump said he was weighing whether the U.S. should join Saudi strikes on the Houthis. "We may. We're going to look at it," he told reporters. "We just found out about the recent attack. So we'll make a decision. We move very quickly."

A Saudi-led coalition has been fighting the Houthis in Yemen as the wider war has spread. Al Jazeera said the Houthis used a ballistic missile and called the strike a dangerous escalation.

The attack is likely to raise Saudi pressure on allies, including the U.S., for more military help.

What we know: 12 people were killed and 309 hurt, including an American.
What we don't: how Saudi Arabia and its allies will respond.