At least 12 people were killed and more than 300 injured Saturday in a major strike on Saudi Arabia's international airport in Riyadh, officials said.

Oct. 10 (UPI) -- At least 12 people were killed and more than 300 injured Saturday in a major strike on Saudi Arabia's international airport in Riyadh.

The Iran-backed Houthi militia claimed responsibility for the attack, which was the largest in a Gulf Arab country since the start of the war in Iran, The New York Times reported.

The death toll at King Khalid International Airport included four Saudi nationals and one U.S. citizen, authorities said. Some of the 309 people injured were in critical condition.

Mohammed al-Bukhaiti, a senior Houthi official, told The Times the attack was in retaliation for Saudi strikes in Yemen.

The official told The Times the attack was launched "so that the world understands that airports, seaports, wedding and mourning halls, hospitals, and markets in Yemen are civilian facilities that must not be targeted or harmed -- and that the same rules that apply to these facilities in Yemen must also apply to their counterparts everywhere else."

April Longley Alley, a senior fellow at the Washington Institute, said the escalating conflict between the Houthis and Saudi Arabia is a major challenge for President Donald Trump.

"The Trump administration wanted to limit the conflict as much as possible, and to keep the lid on it," she told The Washington Post. "But the lid is popping off already."

Trump said he is yet to decide on whether the United States would join Saudi Arabia in its conflict with the Houthis.

"We may," the president told The Post. "We're going to look at it."

The attack came a day after another Houthi strike on the Riyadh airport killed three Saudi citizens.

The militia also claimed responsibility for attacks on infrastructure in Saudi Arabia's south, including an airport in Najran and an airbase near Khamis Mushait.