The morning after a missile struck terminals at Riyadh's King Khalid international airport, the Houthis broke their silence - not to deny the attack, but to warn travellers and airlines against using Saudi airports at all. The message, issued on Sunday, was the group's first public statement since Saturday's strike, which Saudi officials say killed at least 12 people and injured 309.

What Yahya Saree said

Houthi military spokesman Yahya Saree said airports and airspace "are exposed to targeting and constitute a theatre of operations for our forces". He framed the group's campaign as a direct exchange, telling reporters the Houthis were pursuing "airport for airport, siege for siege, and escalation for escalation".

There was one carve-out. Saree said the airports in Mecca and Medina - the holiest cities in Islam - were excepted from the warning.

The strike that prompted the warning

Saturday's attack was the third on Riyadh's main airport that week. The missile made it past Saudi air defences to strike terminals 3 and 4 of King Khalid airport, where hundreds of passengers were waiting for domestic flights.

Saudi officials put the toll at 12 dead and 309 injured, and described the assault as the deadliest in Saudi Arabia in over a decade.

The dead, according to Saudi officials, included:

• •four Saudi citizens
• •two Bangladeshi nationals
• •a Palestinian
• •a US citizen
• •an Egyptian
• •a Jordanian
• •a Syrian
• •a Sudanese

Airspace already tense

The warning did not come out of nowhere. Earlier in the week the Houthis had cautioned commercial airlines "for the last time" about the consequences of flying into Saudi airspace, calling it a theatre of fighting. The main international airport had been targeted for the first time about a fortnight before, as fighting ramped up within Yemen.

In the past month, several carriers had already suspended services to the Saudi capital:

• •Air India
• •FlyDubai
• •Lufthansa Group
• •Pakistan International Airlines

All four had temporarily paused their routes into Riyadh and other Saudi cities. Passengers, too, have been avoiding Saudi Arabia's main international airport since the attack.

Washington weighs in

US President Donald Trump said Washington may join the Saudis in carrying out air strikes against the Iran-backed group in Yemen. Asked about joining the air campaign, he 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."

King Khalid international airport remained closed on Sunday, the day after the attack, with passengers continuing to stay away from the country's main hub. A projectile also fell near the King Fahd international airport in Dammam, according to the Saudi-led coalition - a hub that has been an important alternative to Riyadh amid the recent spate of attacks.