Yemen's Houthi rebel group claims to have orchestrated the drone strike on two Saudi state-run oil refineries that temporarily stalled production on 5% of the world's crude oil.

A United Nations Security Council report from January details the types of drones believed to be used by Houthi forces, including advanced missiles and "so-called 'suicide or kamikaze drones,'" that could be flown from Houthi territory in Yemen to the oil facilities in Saudi Arabia.

A Houthi spokesperson claimed on a Houthi-run TV network that 10 drones were used in the airstrike that reportedly did not cause any casualties, but started fires which have since been controlled, the BBC reports.

The UN panel inspected several UAV-X drones that have been operated by Houthi forces for reconnaissance or attack purposes and have greater distance and lethality capabilities than previous Houthi weapons.

US Secretary of State Mike Pompeo tweeted that there was "no evidence," the attacks came from Yemen, and the US declassified photos of the attack site on Sunday with the intention of providing more evidence that cruise missiles were fired on the oil facilities from northern locations in Iran or Iraq.

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Yemen's Houthi rebel group, part of a regional network of militants backed by Iran, claims to be behind the strikes on two Saudi oil facilities that have the potential to disrupt global oil supplies.

A report from the United Nations Security Council published in January suggests that Houthi forces have obtained more powerful drone weaponry than what was previously available to them, and that the newer drones have the capability to travel greater distances and inflict more harm.

These "so-called 'suicide or kamikaze drones'" include UAV-X drones with a maximum range of 1,500 kilometers, or 930 miles, which would give Houthi forces the ability to launch drones from their Yemen territory to the oil facilities in Saudi Arabia.

Smoke is seen following a fire at an Aramco factory in Abqaiq Reuters

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The drone strikes on Saturday were claimed by the Houthis through spokesperson Brigadier General Yahya Sare'e on a Houthi-controlled TV station. Sare'e said 10 drones were used in the attack, which he said was in retaliation to Saudi military intervention in Yemen that has devastated the country, which has been at war since 2015.

It is still unclear whether Houthi forces are the definite source of the attacks on the Saudi oil facilities. US Secretary of State Mike Pompeo claimed on Twitter that Iran was behind the attacks, which the country's foreign minister denied on Sunday, calling the remarks "maximum deceit," The New York Times reported. The Houthi rebel group is aligned with the Iranian government, which the US believes has trained Houthi forces on drone and missile technology.

Pompeo also said on Twitter that there is "no evidence" the attack came from Yemen. The Saudi Arabian government has not yet issued any statements identifying or accusing a specific attacker. The last drone attack on a Saudi oil facility was carried out by an Iran-backed militia in Iraq.

The US position on the attack is that it stemmed from cruise missiles fired from Iraq or Iran, as opposed to drones sent from Houthi-controlled territory in Yemen. On Sunday, the US declassified photos of the attack site showing strikes on 17 different places, with the intention of providing more evidence for the Iran theory.

The Wall Street Journal also reported that people familiar with the matter said the oil facility was shot by missiles, not drones. The facilities were shown with damage on the sides facing west and northwest, suggesting they may have been hit from Iran, which is situated to the north of the facility, as opposed to Yemen, which is situated to the south.

The strikes caused massive fires to break out in the Saudi government-controlled Aramco company's largest oil processing plant, but the BBC reports the fires have been controlled and no casualties have been recorded.

UN Security Council panels have monitored increased capabilities in recovered Houthi drones since late 2018

An image from the UN Security Council report on munitions used by Houthi forces against Saudi Arabia. United Nations Security Council

If the strikes did originate from Yemen, there is evidence that Houthi forces have obtained drone technology in the last year that is capable of reaching the oil facilities in Saudi Arabia.

According to a panel reporting to the UN Security Council, since September 2018, six drones have been collected that were used by Houthi forces for reconnaissance or attack purposes.

These UAV-X drones contain more powerful engines than the previously studied Qasef-1 drones, which did not allow Houthi rebels to strike further than the southern border regions of Saudi Arabia from Houthi-controlled territory in Yemen.

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However, the Houthi spokesperson claimed that the attack was possible thanks to "cooperation" with people in Saudi Arabia, and warned of further attacks on the country.

The types of drones observed by the UN panel in use by Houthi forces are loitering munitions, which are unmanned aerial vehicles designed to strike targets from a distance using explosive warheads. Not only are UAV-X drones capable of engaging with targets further away, but the warheads examined by the panel contained 18 kilograms, or nearly 40 pounds, of explosives mixed with ball bearings.

Those findings suggest the drones in use by Houthi forces since mid-2018 are more deadly. The weaponry available to Houthi rebels has improved since the Houthi forces have been in collaboration with Iran. Saudi Arabia denied UN requests to inspect the guidance systems of the UAV-X drones, which could indicate supply chains as well as possible violations of the targeted arms embargo on Yemen.

Representatives for Houthi forces and the Saudi Arabia Ministry of Defense didn't immediately respond to Business Insider's request for comment.