Iran-backed Houthi militants in Yemen fired drones and missiles at a number of Saudi Arabia's southern energy facilities Tuesday morning, escalating the fighting on what has become a second front for the kingdom and sending oil prices back toward $100 a barrel.

Saudi Arabia confirmed the attacks, which the Houthis said targeted facilities in Abha, Najran and Jazan. The strikes hit gas and oil storage facilities including at a power plant in Abha and left the major refinery at Jazan aflame and off line, people familiar with the damage said. Output at Jazan had already been diminished by previous Houthi strikes.

Saudi Aramco, the country's majority state-owned oil company, didn't immediately respond to a request for comment.

The attacks come as the U.S.-Iran war, now in its seventh month, continues to crimp energy flows through the Strait of Hormuz. Benchmark Brent crude oil futures rose 1.7% to $98.62 a barrel, having early climbed above $99 a barrel. U.S. oil futures climbed 2.7% to $93.97 a barrel.

Tensions between the Houthis and Saudi Arabia date back to Yemen's civil war, when the kingdom intervened against the militant group, and picked up again in July after a long period of relative calm. The Houthis declared a blockade of Saudi ships in the Red Sea and began attacking the kingdom's oil tankers.

The violence in the Red Sea followed the collapse of a preliminary deal between the U.S. and Iran to open up the Strait of Hormuz and begin winding down the war. Iran attacked ships in Hormuz to assert its control of the waterway, and the Houthi attacks snarled shipments through what had been the Saudis' major alternative route to the blockage in Hormuz.

The escalating violence between the Houthis, Saudi-backed forces in Yemen and the kingdom itself have brought the added risk of disruption to oil processing and production facilities, heightening the risk of further disruption to global energy flows.

"The recent escalation of the Middle East conflict has increased the likelihood of a prolonged standoff, punctuated by calibrated military action by the U.S. and Iran," analysts at ANZ Research said. "This could see Persian Gulf supply remain constrained through the rest of 2026."

Tuesday's attacks caused fires at several locations and led to a halt in some operations while specialized teams worked to contain the fires, secure the sites and assess the damage, the Saudi energy ministry said. It didn't identify the facilities involved or quantify any impact on oil production or exports.

The Houthis also hit the Khamis Mushait Air Base, though the damage was unclear, while their attack on the Jazan airport failed, the people said.

Saudi Aramco's oil facilities in Jazan had already come under attack Monday, the people familiar with the matter said. Aramco was still assessing the damage when the new attack came, they said.

Jazan is home to an Aramco refinery designed to process as much as 400,000 barrels a day of crude oil and produce fuels including gasoline and ultralow-sulfur diesel. Witnesses said it could be seen burning from the city early Tuesday.

Iranian petroleum exports have been shut down by the U.S. Navy. No Iranian crude has crossed the U.S. blockade since mid-July, while the amount of Iranian crude already aboard vessels outside the blockade has fallen to about 29 million barrels from roughly 90 million barrels in mid-July, according to Kpler.