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A week on, it’s still not known who launched the attack on two Saudi oil facilities and from which direction, but the damage is plain to see. Saudi Arabia and the US blame Iran for what appears to have been an attack by 18 drones and seven cruise missiles. Iran denies any involvement but Yemen’s Iran-aligned Houthi rebels have claimed the attack.

What is clear is that the damage caused is significant. Oil prices saw their biggest jump in 30 years on Monday, rising by nearly 15%. Despite this, Saudi Arabia says oil production will resume as normal by the end of September.

The BBC’s security correspondent Frank Gardner was among journalists allowed into the Khurais oil facility and the processing plant at Abqaiq to view the aftermath.

Workers in white overalls, yellow hi-vis jackets and hard hats are still racing to restore the Khurais plant to full capacity after 5.7 million barrels a day were knocked out by the attack on 14 September.

A crane arches up into the air, poised to remove more debris, while small slicks of oil are spread across the concrete apron floor.

Twisted, buckled and blackened by fire, the heavily damaged separation tower at Khurais oilfield stands testimony to one of the most devastating attacks on a country’s critical infrastructure in modern times.

The structure is just one of 19 targets hit by a wave of incoming missiles and explosive-laden drones in the early hours of last Saturday morning.

Both Saudi Arabia and the US have blamed the attack squarely on Iran, which denies it and which had threatened retaliation if it were to suffer a punitive strike.

Saudi Arabia oil attacks: Timeline

• 14 Sept – Two of Saudi Arabia’s major oil facilities, Aramco’s Abqaiq and Khurais, are set ablaze. The Iran-aligned Houthi rebel group says it deployed 10 drones in the attacks. Oil production is cut by 5.7m barrels a day
• 15 Sept – US Secretary of State Mike Pompeo blames the attacks on Iran. Iran accuses the US of “deceit”.
• 16 Sept – Oil prices increase by 15% by the end of the day
• 17 Sept – Saudi Arabia says its oil output will return to normal by the end of September, with half the production already restored. Oil price falls again
• 18 Sept –Saudi Arabia shows off wreckage of weapons which it says proves Iranian involvement

Whoever chose these targets knew exactly what they were doing and programmed the GPS co-ordinates with pinpoint precision.

It was plain to see where the projectiles had hit the separation towers (where the oil and gas are separated out), the large spheroid containers that drain off the water, and various other pieces of steel superstructure, all essential for stabilising the crude oil ready for export.

Processing Saudi Arabia’s natural resource and dispatching it to overseas markets in Europe and Asia is the lifeblood of the Saudi economy. So, billions of dollars have been spent over the decades in providing this country with state-of-the-art defences.

And yet those defences were easily penetrated by these relatively cheap weapons. It’s still not clear exactly who fired them and from where.

When al-Qaeda tried to send an explosive-laden truck into the oil complex at Abqaiq in 2006, it was immediately stopped at the perimeter. But this attack was of a totally different magnitude.

It took the Saudis – and their US allies – completely by surprise, penetrating the security cordon and temporarily knocking out roughly half Saudi Arabia’s processing capacity, sending global oil markets reeling.

Saudi Aramco, the state-owned oil company, says full capacity should be restored by the end of September. But unspoken here is the fear that such an attack could yet be repeated.