US officials familiar with the intelligence on May drone attacks say they originated in Iraq, not Yemen, WSJ reports.

Drone attacks on Saudi Arabia‘s oil industry in May originated in Iraq, not Yemen, US officials have concluded, according to a Wall Street Journal (WSJ) report.

The report, which was published on Friday, drew questions from Iraqi officials who asked Washington for more information supporting the claim.

US officials familiar with the intelligence on the May drone attacks said they had originated in southern Iraq, the WSJ reported, adding that it most likely pointed a finger at Iran-backed armed groups in that region.

Yemen‘s Houthi rebels, who have been battling a Saudi-led military coalition for more than four years, had claimed responsibility for the May 14 drone attacks against the East-West pipeline. The attack forced a brief shutdown but caused no casualties.

The drone attack happened two days after four vessels, including two Saudi oil tankers, were damaged by sabotage off the coast of the United Arab Emirates (UAE).

The suspected attacks took place against a backdrop of US-Iranian tension following Washington’s move last month to try to cut Tehran’s oil exports to zero and beef up its military presence in the Gulf in response to what it called Iranian threats.

There was no immediate comment by the US State Department.

At a weekly news conference on Tuesday, Iraqi Prime Minister Adel Abdul Mahdi told reporters that US officials had contacted Baghdad recently, alleging the drones may have taken off from Iraq.

The prime minister denied the attacks could have come from Iraqi territory.

“All of our intelligence services and our air force denied these reports because the airspace is known,” he said.

“As far as we are concerned, we have no proof and we have no evidence in this matter,” Mahdi added.

He said none of the Iraqi intelligence or military services that monitor its airspace detected any launch.

“There was no movement on that day on this subject,” he said.