Ryad (AFP)

A drone strike against two major Saudi oil facilities has severely disrupted the kingdom's production, provoking renewed tension between Washington and Tehran, which a US official has accused of being behind an "unprecedented attack on energy supplies World ".

Here is what we know of the attacks targeting these two sites of the Saudi oil giant Aramco.

- What is the gravity of the attack? -

Saudi energy infrastructure has already been hit by Yemeni Houthi rebels many times, but the attack is of another magnitude: it targeted Aramco's largest processing plant in Abqaiq, and one of the main oil fields of the public company in Khurais (east). It forced the company to temporarily suspend about half of its production.

However, the extent of the damage and the weapons used remain uncertain. Journalists were not allowed to approach the facilities.

"This will draw attention to the war in Yemen", where Saudi Arabia has been leading an armed coalition since 2015, said James Dorsey, an expert at the Singapore S. Rajaratnam School of International Studies. "This conflict is steadily ceasing to be a war in a lost corner of the Gulf," he adds.

- Who is responsible? -

The Houthi rebels claim to have fired a swarm of drones, in what would be their most ambitious attack.

US Secretary of State Mike Pompeo has accused Tehran. But he did not explain how Iran was involved or where the weapons came from. On Sunday, Iran called the charges "foolish".

US and Saudi officials are investigating, according to the Wall Street Journal, the possibility that the attack was carried out with cruise missiles launched from Iraq or Iran. Baghdad refuted Sunday any link.

- Is global supply affected? -

These attacks, which in their wake reduced global oil supplies by 6%, could drive up the price of oil when markets reopen on Monday. But their impact will depend on how quickly the Saudis resume their production.

The Aramco group said it would draw on its inventory to partially offset the decline.

The incident could undermine investor confidence in the oil giant, which is preparing for a partial IPO. Ryad hopes that this colossal operation will raise up to $ 100 billion, making it the largest operation of its kind.

- Is a wider conflict to be feared? -

If Iran's direct responsibility were established, a new national security puzzle would be announced for Donald Trump, and the nascent inflection of the US position against Tehran would be undermined.

In June, the US president canceled a strike against Iran. Trump is also looking to hold a summit with his Iranian counterpart at the next UN General Assembly, which opens next week in New York.

The strikes will continue to exacerbate the rivalry between Saudi Arabia and Iran, major regional enemies.

The powerful Saudi Crown Prince Mohammed bin Salman said the kingdom was "able" to respond to this "terrorist aggression" without further details.

Dorsey, however, believes that direct retaliation is unlikely since "the Saudis do not want an open conflict with Iran".

If the Houthi's involvement in the attack was proven, the talks that Washington has confirmed to have started this month with the Houthis could be postponed.

- Why does Ryad fail to stop these attacks? -

Saudi Arabia has invested billions of dollars in heavy military equipment, but its arsenal has proved ineffective against the Houthi, a disorganized but highly motivated tribal militia specializing in guerrilla tactics.

Recent developments have also highlighted the significant threat posed by the continued improvement of Houthi armament, from ballistic missiles to unmanned drones.

If the Kingdom's oil wells, spread over a large geographical area, are a difficult target, its treatment facilities are much more exposed.

The Abqaiq factory is the most "vulnerable", according to the Washington-based Center for Strategic and International Studies.

Aramco's extensive network of oil pipelines, pumping stations and terminals along the Gulf and Red Sea is also exposed. In May, the attack of two pumping stations by a drone caused a stoppage of operations of several days.

© 2019 AFP