Saudi Arabia's energy ministry said on Sunday that its key east-west oil pipeline and other facilities had been restored following attacks by Iran on targets across the Gulf.

"Energy facilities and the east-west pipeline damaged by attacks have recovered and regained their operational capacity, enhancing the reliability of supplies," the official Saudi Press Agency reported, citing an energy ministry statement.

Before Tuesday's start of a fragile, two-week truce between Iran and the United States, the Islamic republic had targeted critical energy infrastructure belonging to its oil-rich neighbours.

Tehran accused the Gulf states of allowing US forces to carry out attacks from their territories during the war, which was triggered by Israeli-US strikes on Iran on February 28.

The Gulf states have vehemently denied the Iranian accusations.

Saudi Arabia said operational and technical work had led to "restoring full pumping capacity through the east-west pipeline, amounting to approximately seven million barrels per day".

The energy ministry explained the prior attacks had led to the "loss of approximately 700,000 barrels per day of pumping capacity through the east-west pipeline".

Iran's campaign had impacted output at Saudi's Manifa field, where production was now restored, the ministry said, and at the Khurais oil field, where work was underway to restore full production capacity.

On Friday, Riyadh confirmed the weeks-long Iranian attacks had impacted oil production capacity and killed one person. 

Three people in total have been killed in Saudi Arabia since the start of the war. 

An energy ministry official told the SPA news agency that one of the pumping stations on a vital east-west pipeline was hit in the attacks.

Saudi Arabia's Petroline proved an economic lifeline during the war, with the 750-mile network of pipes connecting the Red Sea to the west with the Gulf in the east as Iran effectively closed the waterway's critical Strait of Hormuz chokepoint.

Facilities in Riyadh, the Eastern Province and the industrial city of Yanbu as well as infrastructure for oil and gas production, transport and refining, and petrochemical plants and power facilities were targeted in the Iranian attacks on Saudi Arabia, the official said.