ISTANBUL — The assault on oil facilities in Saudi Arabia this past weekend has highlighted what analysts say is a rapidly evolving threat from Iranian-made weapons in the region, marking a potentially alarming shift toward precision strikes on critical infrastructure.

U.S. officials believe that cruise missiles and drones were used in the assault and that part of the operation, which was claimed by Yemen’s Houthi rebels, was launched from Iranian territory, according to a U.S. official. Tehran has denied involvement.

“The Yemeni people have a right to respond” to Saudi military aggression, Iranian President Hassan Rouhani said Monday, calling the attack “reciprocal” and “legitimate defense.”

The Saudi Foreign Ministry said in a statement that initial investigations “indicated that the weapons used in the attack were Iranian weapons.” The statement said that Saudi authorities were still working to determine the source of the attack. 

Iran maintains advanced missile and drone programs as part of its national defense strategy and has transferred some of those weapons and technology to allied forces in the region, including Houthi fighters in Yemen, U.S. officials and weapons experts say. Tehran’s drone and missile arsenals allow it to deter adversaries and support regional proxies, who can strike on Iran’s behalf, analysts say.

“The same strategic logic that animates Iran’s missile program is evident in its drone program: It enables Iran to operate from range, keep its territory safe and strike at faraway targets,” said Behnam Ben Taleblu, a senior fellow at the Foundation for Defense of Democracies.

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President Trump publicly discussed Iran three times on Sept. 16, saying "it's looking" the country was behind an attack on Saudi oil fields. (Drea Cornejo/The Washington Post)

“Drones, missiles and rockets all feature into Iran’s asymmetric security strategy and are relatively cheaper to produce,” he said.

According to the Brookings Institution, Iran has become a “significant exporter of missiles, missile production capability and missile technologies,” including a long-range land-attack cruise missile experts say may have been used in Saturday’s assault.

The sophisticated nature of the attack, which targeted sensitive oil installations and took about half of the state oil company’s production offline, signaled a significant departure from previous operations claimed by Houthi rebels or launched by Iranian forces or their proxies in Syria.

Iran and Saudi Arabia are chief rivals in the region, and the Saudi leadership has been a key advocate of the Trump administration’s campaign of “maximum pressure” against Iran. The United States has imposed sanctions on the Iranian economy in a bid to compel Tehran to negotiate constraints on its missile programs and support for regional proxy forces.

“If it is proven that cruise missiles came from Iranian territory, that would be a marked escalation and indicate a measure of confidence that Iran does not fear kinetic reprisal” from either Saudi Arabia or the United States, Taleblu said.

This satellite overview shows damage to oil/gas infrastructure from weekend drone attacks at Abqaig on September 15, 2019 in Saudi Arabia. (Ho/Planet Labs Inc./AFP/Getty Images)

He added: “Iran prefers not to fire from its territory.”

The Trump administration believes that Yemen’s Houthis also contributed to the assault, according to the U.S. official. There were between 17 and 19 direct hits on Saudi oil facilities in Abqaiq and Khurais, about 500 miles from Yemen’s border, the U.S. official said.

Saudi defense systems apparently failed to detect the cruise missiles and drones swarming over its borders, underscoring the kingdom’s vulnerability to asymmetric warfare.

“I’m just surprised that they got caught with their pants down,” a contractor working for the Pentagon on drone defenses said of the Saudi security services. He spoke on the condition of anonymity because he was not authorized to speak to the media.

“They should have seen this coming,” he said.

According to a U.N. expert panel on Yemen, Houthi fighters have in the past used what are known as “suicide” or “kamikaze” drones, some of which are similar to Iranian models. The Houthis have “retained access to the critical components, such as engines, guidance systems, from abroad that are necessary to assemble and deploy them,” the panel’s report said. 

A combined assault using both drones and cruise missiles could in theory “help with confusing and overwhelming defense systems,” offering strategic advantage to the attacker, said Justin Bronk, a research fellow at the London-based Royal United Services Institute.

According to Markus Mueller, an analyst at the German Fraunhofer Group for Defense and Security, radar systems are typically able to identify drones flying over vast stretches of land, especially on even surfaces and outside cities or mountainous areas.

The challenge, said Mueller, whose research focuses on unmanned aerial vehicles, or drones, is to be able to respond to sightings and immediately protect sensitive infrastructure.

But analysts pointed to the alleged use of cruise missiles in the assault, which experts say are low-flying and more difficult to detect, as a worrisome development. The missiles can be precision guided and allow for more devastating strikes on specific targets.

Iran has reverse-engineered a former Soviet land-attack cruise missile, the Kh-55, and has also used Chinese anti-ship missile technology to bolster its own capabilities and those of its proxies, weapons analysts say. During the 2006 war in Lebanon, Iran-backed Hezbollah militants targeted an Israeli vessel with what weapons experts say was probably a Chinese C-802 anti-ship missile provided by Iran.

In its 2018 Worldwide Threat Assessment, the Office of the Director of National Intelligence said that Houthi rebels attempted a cruise missile attack on an unfinished nuclear reactor in Abu Dhabi, the capital of the United Arab Emirates.

Such missiles are “harder to detect and defend against than drones,” said Rawan Shaif, an investigator at Bellingcat, a website specializing in open-source intelligence. “They can be incredibly precise if the person who is guiding them knows what [they] are doing.”

“This was a precision attack,” she said of the assault on the Saudi oil facilities. “It was accurate to a ‘T’ if their aim was to hit” specific infrastructure at the site, Shaif said.

Henry Rome, an analyst at the New York-based political risk firm Eurasia Group, said that if Iran is responsible, its strategy is to “build leverage for eventual talks with Washington.”

Iran wants to “compel the Trump administration to put their foot on the brakes of sanctions and push other countries to stand up for them,” Rome said. The attacks on the oil facilities would be “pushing the limits,” he said. “But it’s too early to say that the guardrails are off.”

Noack reported from Berlin. Steven Mufson and Missy Ryan in Washington contributed to this report.