The United States has concluded the weekend attack on Saudi oil facilities was launched from Iranian soil and cruise missiles were involved, a US official told AFP on Tuesday.

The official, who declined to be identified, said the United States was gathering evidence about the attack to present to the international community, notably European allies, at the UN General Assembly next week.

Asked if Washington was certain that the missiles had been launched from Iranian soil, the official answered: "Yes."

The weekend strikes on Abqaiq — the world's largest oil processing facility -- and the Khurais oil field in eastern Saudi Arabia have roiled global energy markets.

Yemen's Iran-aligned Houthi rebels claimed responsibility for Saturday's attacks but Saudi Arabia accused Iran and President Donald Trump also singled out Tehran.

"Certainly, it would look to most like it was Iran," Trump said Monday.

The U.S. government produced satellite photos showing what officials said were at least 19 points of impact at two Saudi energy facilities, including damage at the heart of the kingdom's crucial oil processing plant at Abqaiq. Officials said the photos show impacts consistent with the attack coming from the direction of Iran or Iraq, rather than from Yemen to the south.

Iran called the U.S. claims "maximum lies" and threatened American forces in the region.

The attack Saturday on Saudi Arabia's Abqaiq plant and its Khurais oil field led to the interruption of an estimated 5.7 million barrels of the kingdom's crude oil production per day, equivalent to more than 5% of the world's daily supply. It remains unclear how King Salman and his assertive son, Crown Prince Mohammed bin Salman, will respond to an attack targeting the heart of the Saudi oil industry.