Saudi Arabia said on Tuesday that drones laden with explosives, evidently launched from Yemen by the Iran-backed Houthi insurgency, attacked two of its oil pumping stations.

A team of U.S. military investigators reportedly believes Iran or its proxies orchestrated the bomb attacks on four commercial vessels anchored off the coast of the United Arab Emirates on Sunday, two of them Saudi oil tankers.

Saudi Energy Minister Khalid al-Falih linked the drone attacks to the tanker bombings, describing them as a plot to jeopardize the world’s oil supply.

“These attacks prove again that it is important for us to face terrorist entities, including the Houthi militias in Yemen that are backed by Iran,” he said.

Falih denounced the drone attack as “cowardly” and an “act of terrorism.”

The foreign ministry of the United Arab Emirates also condemned the attack as “new proof of the Houthis’ hostile and terrorist tendencies.” Bahrain’s foreign ministry denounced it as a “cowardly” threat against “the safety of the world’s energy supply.”

A statement from the Saudi Aramco oil company described the damage as minimal and quickly contained:

Saudi Aramco responded to a fire at East West Pipeline Pump station 8 which was caused by a sabotage incident using armed drones which targeted pump stations 8 and 9. As a precautionary measure, the company temporarily shut down the pipeline, and contained the fire which caused minor damage to pump station 8. Saudi Aramco confirms that no injuries or fatalities have been reported. Saudi Aramco’s oil and gas supplies have not been impacted as a result of this incident.

Oil prices nevertheless jumped on Tuesday morning after news of the drone attack coming soon after the weekend’s oil tanker sabotage.

Houthi-run media in Yemen took credit for the attack, portraying it as a “big military operation” against “vital” Saudi oil facilities carried out in response to the kingdom’s “continued aggression and blockade” of Yemen.

The Jerusalem Post noted the Houthis have a history of using drones provided by Iran:

This is not the first time the Houthis have used drones. Since 2017 reports have indicated that Houthi drones are Iranian-made or based on Iranian designed. In recent years Iran has sought to expand its drone arm, either copying captured western drones or creating its own armed and unarmed models.

The Houthis have been selected by Iran as a good place to test out the drone capabilities against a Western-backed army like the Saudis who use U.S. and other Western equipment. An Iranian drone penetrated Israeli airspace in February of 2018 and was shot down. It is part of the wider regional contest between Iran, its allies and Iran’s adversaries. Drones are a key component of this conflict.

Iranian media thinks the drone strikes are important because it burnishes Iran’s image and shows that Iranian backing, even if Iran doesn’t take direct credit for that backing, is aiding the Houthis.

Fox News quoted a source on Monday night who said a U.S. military team has examined the four commercial vessels damaged by explosions off the coast of the UAE on Sunday and concluded agents of Iran or its proxy forces attacked them. The source said each of the four ships had a similar hole near the waterline between five and ten feet in diameter.

Officials at the UAE port of Fujairah said on Tuesday limpet mines, explosive devices attached to the hull of a targeted vessel by magnets, appeared to damage the ships. Reports found the port operating normally on Tuesday despite elevated security warnings.

President Donald Trump responded to news of the oil tanker bombings on Monday by threatening Iran with dire consequences for sabotage and terrorism.

“It’s going to be a bad problem for Iran if something happens, I can tell you that. They’re not going to be happy,” Trump told reporters, assuring them the Iranian government knows exactly what he means by “bad problem.”

The Gulf Cooperation Council condemned the tanker sabotage on Monday as a “serious escalation” that could “increase tensions and conflict in the region and jeopardize the interests of their peoples.”

Iran stepped up its efforts to deflect blame for the tanker bombings on Tuesday by suggesting they were a false-flag operation conducted by Israel.

“The events that took place in the Emirates were Israeli mischief,” declared Iranian parliamentary spokesman Behrouz Nemati, without providing any evidence for the allegation.