Several explosions have been reported in the Saudi capital of Riyadh, disrupting flights and triggering air raid warnings amid escalating hostilities with Yemen’s Houthis.

Saudi authorities sent emergency alerts early on Saturday warning residents of a “hostile aerial threat” and urging them to remain indoors, according to several media outlets. Explosions were reportedly heard across the city before the civil defense agency issued an all-clear about half an hour later. It was the first such warning in Riyadh since fighting in neighboring Yemen intensified in July.

Later on Saturday, a large plume of black smoke and flames was seen near King Khalid International Airport. Reuters footage showed smoke rising from the airport’s fuel-storage area, while flight-tracking service Flightradar24 reported major delays and cancellations. Saudi authorities have not disclosed the cause of the explosions or provided details on casualties or damage.

The latest escalation began in July after Saudi strikes on Yemen's Sanaa International Airport shattered a fragile truce dating back to 2022, prompting a renewed exchange of attacks with the Houthis.

The Houthis, who control much of northern Yemen, have made significant territorial gains in recent weeks, advancing along the Red Sea coast and seizing strategic positions around the Bab el-Mandeb Strait, one of the world’s most important maritime chokepoints.

The advances have put further pressure on Saudi Arabia’s oil exports. Riyadh has increasingly relied on Red Sea routes as shipping through the Strait of Hormuz has been disrupted by the US war on Iran.

Maritime tracking data cited by AFP showed Saudi exports through the waterway have declined since July, although several loaded vessels passed through over the past week. The Houthis say international shipping remains unaffected, with the exception of Saudi vessels.

The disruption has already hit crude supplies. State oil giant Saudi Aramco has told European refiners they will receive no crude in October, Bloomberg reported on Friday, as oil prices hover above $100 a barrel.