The number of attacks by the Iran-backed Houthi militia in Yemen on Saudi Arabia, predominantly targeting civilian locations, doubled during the first nine months of 2021 compared with the same period a year earlier, according to research by a US think tank.

The report, by the Center for Strategic and International Studies in Washington, also called on the US to provide Saudi Arabia with additional aid to defend itself against the attacks, and to highlight the key role Iran plays in facilitating them.

“Iran and Ansar Allah (Partisans of God), better known as the Houthi movement, have conducted a campaign of high-profile attacks against civilian Saudi Arabian and coalition targets in the Gulf,” according to the CSIS report, which was released on Tuesday.

“The Houthis are orchestrating an increasingly intense irregular warfare campaign against Saudi Arabia and other countries in the Gulf using sophisticated cruise and ballistic missiles, UAVs (unmanned aerial vehicles, commonly known as drones), and other stand-off weapons.”

CSIS studied a total of 4,103 attacks from within Yemen on Saudi locations, and against maritime and other targets, between Jan. 1, 2016, and Oct. 20, 2021. It found that “the number of Houthi attacks per month doubled against Saudi Arabia and other targets over the first nine months of 2021 compared to the same period in 2020.”

It also found that Iran’s Islamic Revolutionary Guards Corps, which answers directly to the country’s supreme leader, “has provided the Houthis with training and a growing arsenal of sophisticated weapons and technology for anti-tank guided missiles, sea mines, explosive-laden UAVs, ballistic and cruise missiles, unmanned maritime vehicles, and other weapons and systems.”

The report noted that the Quds Force, the expeditionary arm of the IRGC, worked alongside Lebanese Hezbollah to improve Houthi capabilities “at a relatively low cost,” especially, it adds, when compared with the cost to Saudi Arabia of improving the air defenses required to negate the threat posed by missile and drone attacks.

“The United States and its allies should conduct a more aggressive campaign to publicly highlight Iranian and Houthi actions and provide additional security assistance to Saudi Arabia and other Gulf states,” it said.

Yemen, the poorest country in the Arab world, was plunged into conflict in 2014 when the Houthis, ideologically aligned with Tehran, violently seized the country in a coup against the internationally recognized government. Saudi Arabia subsequently intervened, alongside an international coalition, against the Houthis and in defense of the UN-backed Yemeni government.

“Not only has there been a rise in the number of attacks against Saudi Arabia over the past year, but Iran and Lebanese Hezbollah continue to provide the Houthis with increasingly sophisticated weapons systems,” the CSIS warned.

“The Houthis now have a growing assortment of cruise and ballistic missiles, UAVs and other stand-off weapons capable of striking targets throughout the Gulf — and beyond.”

One way that Washington could continue to support the Kingdom is by ensuring supplies of Patriot surface-to-air missiles remain forthcoming, according to the report. In addition, it said, the US “should provide additional counter-UAV technology, since Patriot systems have limited utility against small UAVs.”

This would help to mitigate the threat of attacks using small drones, which have become increasingly prevalent this year.

But while counter-drone technology would reduce the physical threat to Saudis it is also key, said the CSIS, that the international community is made more aware of the key role Tehran plays in stoking the flames of war in Yemen.

“Growing public awareness of the extent of Iranian support for the Houthis could also put pressure on multilateral organizations, such as the United Nations, to condemn Iranian intervention more forcefully in the conflict and demand that the Houthis renounce Iranian support as a part of peace negotiations,” according to the report.

In a final warning, the CSIS said: “Without a more effective campaign to publicly highlight and counter these attacks and help Saudi Arabia defend itself, however, Iran and the Houthis will continue to destabilize the region.”