Saudi Arabia raced Sunday to restore crude production knocked out by a weekend attack, but the blow at the heart of the kingdom’s oil industry threatens to boost prices and raise concerns about the security of supplies in the region.

Analysts said they were looking ahead to the opening of futures-market trading Sunday evening to see how much oil prices would react, but that it was hard to assess without more details about the longer-term disruption to Saudi production.

“The oil price could move up $5 to $10 a barrel if it turns out the damage is extensive,” said Andy Lipow, president of Houston-based consulting firm Lipow Oil Associates.

Saudi officials said they could return to normal levels of oil production by Monday, after an attack Saturday disabled a key processing plant and knocked out about five million barrels of production—about half of the country’s output and 5% of global supply.

Western capitals said they were ready to release emergency stocks if necessary, and Saudi officials discussed shipping their own extra inventory to meet short-term supply needs, according to people familiar with the matter.


The International Energy Agency, a Paris-based group representing top energy-consuming nations that coordinates such releases, said it was in contact with Saudi authorities and major producer and consumer nations.

“For now, markets are well supplied with ample commercial stocks,” the group said. “The IEA is monitoring the situation in Saudi Arabia closely.”

Markets haven’t seen a shutdown on this scale since Iraq invaded Kuwait in 1990. That conflict, which led to an international military intervention, saw the loss of four million barrels a day.

The IEA last carried out an emergency release of its strategic reserves when a Libyan civil war in 2011 took out production capacity of 1.7 million barrels a day. The U.S., with its Strategic Petroleum Reserve, often acts alongside the IEA, but could also act on its own.


The U.S. is now the world’s largest crude producer and among the top exporters of oil and gas. For the first time in decades, President Trump would be in position to help stabilize the oil market in the event of a prolonged outage—a remarkable turnaround from the 1990s and 2000s, when the country was far more dependent on foreign crude.

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Before strike, left. After strike, right, where a satellite image from Planet Labs Inc. shows black smoke rising from Saudi Aramco's Abqaiq oil processing facility after it was hit. Photo: Planet Labs via Associated Press

While the U.S. still imports significant volumes, including from Saudi Arabia, Mr. Trump could authorize an emergency release of stockpiled crude that could help mitigate price increases, analysts said. The U.S. reserve holds more than 600 million barrels of oil. He could also temporarily ease sanctions on Venezuela or Iran, or alter trade restrictions that have affected U.S. crude exports.

The U.S. also has the capability to lift output at home. A significant boost in prices would be a shot in the arm for shale producers, who have been under tremendous pressure from investors to restrain spending and focus on profits.

But sustained Saudi outage of several million daily barrels would rattle markets, because of a lack of other players big enough to step in and provide enough supply to cover such a shortfall longer term.


And even if Saudi officials are successful in restoring all or most production, the attack demonstrates a new, wider vulnerability of supply lines across the oil-rich Gulf.

Tankers have been paying sharply higher insurance premiums, while shipping rates have soared in the region after a series of maritime attacks on oil-laden vessels blamed by the U.S. on Iran. Washington said it believed Iran was to blame for the Saturday attack, a charge Tehran has denied.

The attacks Saturday hit Hijra Khurais, one of Saudi Arabia’s largest oil fields producing about 1.5 million barrels a day, and Abqaiq, the world’s biggest crude stabilization facility, which processes seven million barrels of Saudi oil a day. It is where the Saudi industry turns crude oil into specific grades, such as Arabian Extra Light, requested by customers.

Saudi Arabia has also long been the target of attacks from Iranian-aligned Houthi rebels in Yemen, who claimed the weekend attack. But the country had until now avoided an attack that shuttered such a big chunk of production.


“It’s the mother ship of the Saudi energy system,” said Helima Croft, global head of commodity strategy at RBC Capital Markets. “This is probably the worst infrastructure attack we’ve seen in the kingdom.”

Underscoring the heightened risks, a tanker owned by Bahri, the Saudi Arabian oil shipper, had increased its security while sailing in the Persian Gulf Saturday, according to the vessel’s captain. Safety measures included creating a restricted area on the shore side of the ship, deterring waterside access to the ship and additional security briefings to the crew.

Saudi Arabia’s state owned oil company Aramco has long been known for robust redundancy measures, which may help the country quickly restore production. The attack will be a crucial test for how effective those redundancies are.

The Ghawar field, the world’s largest, and the Shaybah field, which produces a million barrels a day, also reported disruptions due to Abqaiq’s problems, people familiar with the matter said.

The attacks are the latest assaults in recent months by the Houthis and Iranian-backed armed groups in Iraq, which have hit Saudi airports, a desalination plant and oil infrastructure. Since the Houthis took control of Yemen’s capital, San’a, in 2014 in a civil war, a Saudi-led coalition has fought to reinstate a government there supported by regional powers.

Tensions between Iran and the U.S. and its allies including Saudi Arabia have helped push the price of Brent crude, the global benchmark, up 12% to $60 a barrel this year. Oil is still well below its April highs on worries that softening demand will result in a supply glut. U.S. crude is at about $55 a barrel.

Write to Benoit Faucon at benoit.faucon@wsj.com, Summer Said at summer.said@wsj.com and Amrith Ramkumar at amrith.ramkumar@wsj.com