Saudi Arabia's energy ministry said some operations at its massive Ras Tanura refinery on the Gulf coast had been halted on Monday, following an attack that caused a fire at the complex.
The Ras Tanura facility along the kingdom's eastern Gulf coast is home to one of the largest refineries in the entire Middle East and a cornerstone of the kingdom's energy sector.
The complex has a capacity of 550,000 barrels per day.
"Some operational units at the refinery were shut down as a precautionary measure, without any impact on the supply of petroleum products to local markets," an official source at the ministry said in a statement published by the Saudi Press Agency.
Earlier, a source familiar with the incident told AFP the attack caused a fire at the Ras Tanura refinery, but the blaze had already been extinguished.
A Saudi defence ministry spokesman said two drones had targeted the refinery and been intercepted, according to a statement posted by the Saudi Press Agency on X.
The complex also serves as one of the world's biggest oil ports.
Torbjorn Soltvedt, an analyst at risk intelligence company Verisk Maplecroft, said the incident marked a major uptick in tensions in the Gulf following a spate of attacks by Iran across the region.
"The attack on Saudi Arabia’s Ras Tanura refinery marks a significant escalation, with Gulf energy infrastructure now squarely in Iran’s sights," said Soltvedt in a note on the conflict.
"The attack is also likely to move Saudi Arabia and neighbouring Gulf states closer to joining US and Israeli military operations against Iran."
Saudi Arabia lambasted Iran over the weekend after Iran targeted Riyadh and its eastern region with strikes, warning it reserved the right to defend itself including by retaliating.
Saudi oil infrastructure has been targeted in the past by Iranian-backed Houthi rebels.
In March 2022, the Houthis launched a drone attack targeting the YASREF refinery in Yanbu Industrial City on the Red Sea.
And in 2019, Houthi-claimed aerial assaults on two Aramco facilities in eastern Saudi Arabia temporarily knocked out half of the kingdom's crude production.