The Saudi and Yemeni capitals were rocked by new strikes on Sunday, a day after the Iran-backed Houthi militia carried out a devastating attack on the Saudi capital’s airport, the kingdom’s deadliest attack in over a decade.

Maj. Gen. Turki al-Maliki, a spokesman for the Saudi-led military coalition in Yemen, said on social media that an “unidentified projectile” had struck the airport in Saudi Arabia’s capital, Riyadh, causing a fire on Sunday. The Saudi civil aviation authority said early Monday that one person, a Pakistani resident, was killed and 11 injured in the latest strike at the airport, King Khalid International. The attack also caused damage that was still being assessed, it said.

In Yemen, Houthi-run media reported on Sunday that Saudi aircraft had struck the international airport in the Yemeni capital, Sanaa. The Houthi-run health ministry said that a child had also been killed in a strike on a residential building in the capital. Saudi airstrikes have killed 91 people since Sept. 3, mostly women and children, according to Anees al-Asbahi, a spokesman for the ministry.

The Houthi attacks on the airport in Riyadh come amid a spate of increasingly brazen strikes by the militia on vital Saudi infrastructure in recent days, which have rattled the kingdom and frayed nerves in its capital.

King Fahd International in Dammam, a major airport in the kingdom’s east, was also attacked on Sunday, the Saudi civil aviation authority said, adding that a damage assessment was underway without further details.

The Houthi military spokesman, Yahya Saree, on Sunday said that an operation aimed at the airport in Dammam had hit the site and “disrupted air traffic.”

The U.S. Embassy in Saudi Arabia said in an alert that it was aware of the attacks on Sunday on the airports, warning government employees to exercise “extreme caution when using all major airports” and requiring special authorization to use of those in Riyadh, Dammam and Jeddah. The embassy also barred any “travel within 20 miles of the Yemen border due to safety risks.”

A day earlier, the strike by the Houthis on a passenger terminal at the airport in Riyadh marked the deadliest attack in a Gulf Arab country since the U.S.-Israeli war with Iran began in February. That strike killed at least 12 people and injured hundreds, the Saudi authorities said. On Sunday, the Indian Embassy in Saudi Arabia said an Indian national injured in the attack had also died.

Saudi officials did not specify the nature of the attack on Saturday, but a Gulf official and a U.S. official briefed on the strike said that the Houthis had struck the airport with a cruise missile.

The latest escalation between Saudi Arabia and the Houthis began in July, when the militia accused Saudi Arabia of bombing Sanaa airport while an Iranian plane was trying to land. Fighting intensified last month with the Houthis seizing Yemen’s Red Sea coast from the Saudi-supported government. Backed by Saudi warplanes, Yemeni government forces launched a counteroffensive last week, plunging the country back into a full-blown war

The metastasizing conflict, which has imperiled Saudi Arabia’s ambitions to become a global business and tourism hub, has eroded the sense of security that Saudis had largely maintained through years of war in neighboring Yemen. On Sunday, schools across Riyadh notified parents that in-person lessons would be canceled for the week. Many workplaces also told employees they could work from home.

Racked by years of conflict, the Houthis have little to lose by comparison and have become battle-hardened after repeated confrontations with more powerful, wealthier enemies.

With financial and military support from Iran, the Houthis have invested heavily in weapons manufacturing in recent years, allowing them to mount increasingly sophisticated cross-border strikes, analysts say.

Shuaib Almosawa contributed reporting from Sanaa, Yemen and Ephrat Livni from New York.