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.

relates to Yemen’s Houthis Claim Strike on Saudi Base, Aramco Oil Depot

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%.

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.

Read more: U.S. Labels Houthis Terrorists After Attacks on Oil Tankers

Former U.S. President Donald Trump classified the Houthis as a terrorist organization last year, shortly after a number of attacks on oil tankers in the Red Sea. Biden rescinded that designation, saying it was hindering the efforts of aid workers to provide food and shelter to Yemenis living under Houthi control.

Biden’s administration has vowed to end the conflict. Last month, it halted U.S. support for Saudi Arabia’s offensive operations and appointed Tim Lenderking, a former senior State Department official, to lead American peace efforts.

The Houthis have had indirect talks with American officials, Mohammed Bakhiti, a member of the group’s political bureau, told Al Jazeera on Thursday. They haven’t resulted in any progress, he said.

“As long as the aggression and blockade continue, we will respond with full force,” he said.