Yemen’s Houthi rebels said they launched missile and drone strikes against a Saudi Arabian oil facility and a military base, as their attacks on the kingdom’s energy and security installations multiply.

The Houthis, who are backed by Iran in Yemen’s civil war, said they bombed King Khalid Air Base in Saudi Arabia’s southwestern city of Khamis Mushait with a drone and hit a Saudi Aramco fuel depot in Jeddah with a Quds-2 cruise missile.

Saudi officials also said they intercepted a “ballistic missile fired by the terrorist Houthi militia” toward Jazan, a city on the Red Sea coast near the Yemeni border and south of Jeddah.

The extent of the damage, if any, was not immediately clear for any of the three locations.

While most of the strikes claimed by the Houthis cause limited damage and few casualties, their frequency has roiled energy and shipping markets in the oil-rich Persian Gulf. Brent crude rose 0.7% to $64.50 a barrel on Thursday, extending this year’s gains to 25%.

Aramco and Saudi officials did not immediately respond to requests for comment on the claimed Aramco attack.

Tensions have mounted in the Gulf as U.S. President Joe Biden explores rejoining a 2015 accord designed to reduce Iran’s nuclear activities. The Pentagon said on Wednesday it may respond to a rocket assault on a base in western Iraq hosting its troops. While no group has yet claimed responsibility, the U.S. blamed Iran for an attack on the site last year.

Washington carried out air strikes against Iran-backed fighters in Syria late last month in reaction to an attack on a military base in northern Iraq. Biden said that was a warning to Iran to “be careful.”

Yemen War

The Houthis have been fighting Yemen’s United Nations-recognized government since 2014. A Saudi-led coalition intervened the following year on the side of the government. The UN has called the conflict — in which tens of thousands of people have died — the world’s worst humanitarian crisis.