A report by United Nations sanctions monitors has said Yemen's Houthi rebels did not carry out an attack in September that set ablaze two major Saudi oil facilities, Reuters news agency reported.

The United States, European countries and Saudi Arabia accused Iran of being behind the attack on Saudi Aramco oil plants in Abqaiq and Khurais that was claimed by the Houthis. Iran has denied any involvement.

More:

According to the report seen by Reuters on Wednesday, the independent UN experts to the Security Council Yemen sanctions committee said: "That despite their claims to the contrary, the Houthi forces did not launch the attacks on Abqaiq and Khurais on 14 September 2019."

Riyadh, which is backing Yemen's internationally recognised government in its fight against the Houthis, has long accused Iran of supplying the rebels with weapons. Tehran says it supports the rebels diplomatically and politically but has repeatedly denied providing them with any military aid.

The reported findings by the UN monitors come amid escalating tensions in the region after the US assassinated top Iranian military commander Qassem Soleimani in Iraq last week and Tehran retaliated on Wednesday by firing missiles at Iraqi bases housing US troops.

The UN investigators said they doubted that the drones and land-attack cruise missiles used in the September 14 attack "have a sufficient range to have been launched from Yemeni territory under the control of the Houthis."

"The panel notes that Abqaiq and Khurais were approached respectively from a north/northwestern and north/northeastern direction, rather than from the south, as one would expect in the case of a launch from Yemeni territory," the report said, according to Reuters.

The investigators, who monitor sanctions on Yemen, also said they do not believe that "those comparatively sophisticated weapons were developed and manufactured in Yemen." They were not tasked with identifying who was responsible for the Saudi attack.

The attacks that targeted the Abqaiq and Khurais oil plants caused an increase in oil prices and shut down more than 5 percent of global oil supply. Saudi Arabia said on October 3 that it had fully restored oil output.

The Saudi minister of state for foreign affairs, Adel al-Jubeir, signalled in September that Riyadh was waiting for results of UN investigations before announcing how his country would respond.

UN experts monitoring UN sanctions on Iran and Yemen travelled to Saudi Arabia days after the September attack.

Antonio Guterres, the UN secretary-general, told the Security Council in a separate report on December 10 that the UN was "unable to independently corroborate" that missiles and drones used in the attacks "are of Iranian origin".

The report is from the independent panel of experts that reports twice a year to the Security Council on the implementation of sanctions related to the conflict in Yemen that were imposed in 2014 and 2015.

It was submitted to the UN Security Council Yemen sanctions committee on December 27, but will not be made public for a few more weeks.

"The Houthi forces continue to receive military support in the form of assault rifles, rocket-propelled grenade launchers, anti-tank guided missiles, as well as more sophisticated cruise missile systems," the report found.

"Some of those weapons have technical characteristics similar to arms manufactured in Iran," it said.

A Saudi-UAE-led military coalition intervened in Yemen's conflict in 2015 in support of forces loyal to President Abd-Rabbu Mansour Hadi, who had been forced out by the Houthis.

Since then, tens of thousands of people have been killed and millions driven to the brink of famine in a war the UN calls the world's worst humanitarian crisis.