Drones launched by Yemen’s Houthi rebels have attacked the world’s largest oil processing facility in Saudi Arabia and another major oilfield, sparking huge fires.
It remains unclear whether anyone was injured at the Abqaiq oil processing facility and the Khurais oilfield, or what effect the assault will have on global oil production.
Rising smoke from fires at the sites could be seen by satellites in space.
US president Donald Trump called Saudi Arabia’s Crown Prince Mohammed bin Salman in the wake of the drone strikes and expressed the United States’ readiness to cooperate with the kingdom in supporting its security and stability, according to the Saudi embassy in Washington.
Mr Trump said recent attacks against Saudi state-run oil facilities have had a negative impact on the US and global economies.
The crown prince assured the US leader that Saudi Arabia is “willing and able to confront and deal with this terrorist aggression”.
The attack by the Iranian-backed Houthis in the war against a Saudi-led coalition comes after weeks of similar drone assaults on the kingdom’s oil infrastructure, but none of the earlier strikes appear to have caused the same amount of damage.
The US has blamed Iran, with secretary of state Mike Pompeo tweeting, “There is no evidence the attacks came from Yemen.
“Iran has now launched an unprecedented attack on the world’s energy supply.”
The attack will likely heighten tensions further across the wider Persian Gulf amid a confrontation between the US and Iran over its unravelling nuclear deal with world powers.
Initial reports of the assault came in online videos of giant fires at the Abqaiq facility, some 205 miles north-east of the Saudi capital, Riyadh.
Machine gun fire could be heard in several clips alongside the day’s first Muslim call to prayers, suggesting security forces tried to bring down the drones in the darkness just before dawn.
In daylight, Saudi state television aired a segment with its local correspondent near a police checkpoint, with a thick plume of smoke visible behind him.
The fires began after the sites were targeted by drones, the interior ministry said in a statement carried by the state-run Saudi Press Agency. An investigation is under way.
Saudi Aramco, the state-owned oil giant, did not respond to questions from The Associated Press. The kingdom hopes soon to offer a sliver of the company in an initial public offering.
In a short address aired by the Houthi’s Al-Masirah satellite news channel, military spokesman Yahia Sarie said the rebels launched 10 drones in a coordinated attack on the sites after receiving “intelligence” support from those inside the kingdom.
He warned that attacks by the rebels would only get worse if the war continues.
“The only option for the Saudi government is to stop attacking us,” Mr Sarie said.
The rebels hold Yemen’s capital, Sanaa, and other territory in the Arab world’s poorest country.
Since 2015, a Saudi-led coalition has fought to reinstate the internationally recognised Yemeni government.
The US embassy in Riyadh said it is unaware of any injuries to Americans. Saudi Aramco employs a number of US citizens, some of whom live in guarded compounds in the kingdom near the site.
“These attacks against critical infrastructure endanger civilians, are unacceptable, and sooner or later will result in innocent lives being lost,” US ambassador John Abizaid, a former army general, said.
Saudi Aramco describes its Abqaiq oil processing facility in Buqyaq as “the largest crude oil stabilisation plant in the world”.
The facility processes sour crude oil into sweet crude, then transports it onto trans-shipment points on the Persian Gulf and the Red Sea or to refineries for local production.
Estimates suggest it can process up to seven million barrels of crude oil a day. By comparison, Saudi Arabia produced 9.65 million barrels of crude oil a day in July.
The plant has been targeted in the past by militants. Suicide bombers claimed by al Qaida failed in an attempt to attack the oil complex in February 2006.
The Khurais oil field is believed to produce more than one million barrels of crude oil a day.
It has estimated reserves of more than 20 billion barrels of oil, according to Aramco.
There was no immediate impact on global oil prices as markets were closed for the weekend. Benchmark Brent crude had been trading at just above 60 dollars a barrel.
While Saudi Arabia has taken steps to protect itself and its oil infrastructure, analysts had warned that Abqaiq remained particularly vulnerable.
The Rapidan Energy Group, a Washington-based advisory group, warned in May that “a successful attack could lead to a months-long disruption of most Saudi production and nearly all spare production”.
It called the facility, close to the eastern Saudi city of Dammam, “the most important oil facility in the world”.
Abqaiq “is a systemic vulnerability that cannot be quickly repaired, replaced or circumvented,” the firm warned.
The Washington-based Centre for Strategic and International Studies separately issued its own warning just last month.
“Though the Abqaiq facility is large, the stabilisation process is concentrated in specific areas including storage tanks and processing and compressor trains – which greatly increases the likelihood of a strike successfully disrupting or destroying its operations,” the centre said.
The war has become the world’s worst humanitarian crisis. The violence has pushed Yemen to the brink of famine and killed more than 90,000 people since 2015, according to US figures.
Since the start of the Saudi-led war, Houthi rebels have been using drones in combat.
The first appeared to be off-the-shelf, hobby-kit-style drones. Later, versions nearly identical to Iranian models turned up. Iran denies supplying the Houthis with weapons, although the UN, the West and Gulf Arab nations contradicted this.