Saudi Arabia’s Energy Minister, Prince Abdulaziz bin Salman, said on Monday that the kingdom’s infrastructure had been tested and promised a firm response to deadly attacks by Yemen’s Houthis.

“The events of recent weeks are serious, our response must be equally serious,” he told a conference in Riyadh. He also said: “Energy security can’t be taken for granted.”

An attack on Riyadh’s King Khalid International Airport at the weekend killed 13 people and wounded hundreds, according to Saudi authorities. The civil aviation authority put the number of wounded at 309. A further strike on Sunday killed one person, and airport operations were suspended.

The Houthis claimed several attacks and threatened to keep targeting Saudi transit hubs. The civil aviation authority also reported an attack on Dammam airport. The Saudi-led coalition said it intercepted a Houthi ballistic missile heading for Khamis Mushait.

The coalition has called the airport attack a war crime and said it would respond decisively. Iran, which backs the Houthis, said it was deeply concerned about the escalation.