Drones claimed by Yemen’s Houthi rebels have attacked the world’s largest oil processing facility in Saudi Arabia and a major oilfield operated by Saudi Aramco.
The attacks sparked a huge fire at a processor crucial to global energy supplies.
It was not clear if there were any injuries in the attacks in Buqyaq and the Khurais oil field, nor what effect it would have on oil production in the kingdom.
The attack will also 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.
The Houthis are backed by Tehran amid a Saudi-led war against them in Yemen.
Online videos apparently shot in Buqyaq included the sound of gunfire in the background.
Smoke rose over the skyline and glowing flames could be seen a distance away at the Abqaiq oil processing facility.
The Saudi-owned satellite news channel Al-Arabiya later aired a segment with a correspondent there as smoke from the blazes clearly rose behind.
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.
It said an investigation into the attack was under way.
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 their coordinated attack on the sites. He warned 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.
Saudi Aramco, the state-owned oil giant, did not immediately respond to questions from The Associated Press. The kingdom hopes soon to offer a portion of the company in an initial public offering.
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 later transports onto transshipment points on the Persian Gulf and the Red Sea.
Estimates suggest it can process up to seven million barrels of crude oil a day.
The plant has been targeted in the past by militants. Al Qaeda-claimed suicide bombers tried but failed to attack the oil complex in February 2006.
The Khurais oil field is believed to produce over one million barrels of crude oil a day. It has estimated reserves of over 20 billion barrels of oil, according to Aramco.
There was no immediate impact on global oil prices as markets were closed for the weekend across the world.
Buqyaq is some 205 miles north east of the Saudi capital, Riyadh.
The Saudi-led coalition has been battling the rebels since March 2015. The Iranian-backed Houthis hold Yemen’s capital, Sanaa, and other territory in the Arab world’s poorest country.
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 the US-based Armed Conflict Location & Event Data Project, which tracks the conflict.