Iran's chancellor Mohammad Javad Zarif attends a press conference at the Nicaraguan State Department in Managua, Nicaragua on August 23, 2016. 
Iran's chancellor Mohammad Javad Zarif is traveling with a large delegation of officials and business executives to Latin America intrested in participate in Nicaragua's new interoceanic channel project among others.  / AFP / AlfredoZuniga        (Photo credit should read ALFREDOZUNIGA/AFP/Getty Images)
ALFREDOZUNIGA/AFP/AFP/Getty Images
Iran's chancellor Mohammad Javad Zarif attends a press conference at the Nicaraguan State Department in Managua, Nicaragua on August 23, 2016. Iran's chancellor Mohammad Javad Zarif is traveling with a large delegation of officials and business executives to Latin America intrested in participate in Nicaragua's new interoceanic channel project among others. / AFP / AlfredoZuniga (Photo credit should read ALFREDOZUNIGA/AFP/Getty Images)
Now playing
02:10
Reporter: 'Startlingly dangerous moment' in Middle East
Iran's new President-elect Ebrahim Raisi speaks during a press conference in Tehran, Iran, Monday, June 21, 2021. (AP Photo/Vahid Salemi)
Vahid Salemi/AP
Iran's new President-elect Ebrahim Raisi speaks during a press conference in Tehran, Iran, Monday, June 21, 2021. (AP Photo/Vahid Salemi)
Now playing
02:28
CNN asked Iran's President-Elect about nuclear deal. Hear his reply
Now playing
02:15
See where Olympians will eat, sleep and relax in Tokyo
TABRIZ, IRAN - JUNE 16: Iran presidential candidate Ebrahim Raeesi takes part in a campaign meeting with Residents of Tabriz on June 16, 2021 in Tabriz, Iran. The country's incumbent president, Hassan Rouhani, is ineligible to run again after serving two terms in office. (Photo by Meghdad Madadi ATPImages/Getty Images)
ATPImages/Getty Images Europe/Getty Images
TABRIZ, IRAN - JUNE 16: Iran presidential candidate Ebrahim Raeesi takes part in a campaign meeting with Residents of Tabriz on June 16, 2021 in Tabriz, Iran. The country's incumbent president, Hassan Rouhani, is ineligible to run again after serving two terms in office. (Photo by Meghdad Madadi ATPImages/Getty Images)
Now playing
02:20
Ultra-conservative candidate wins Iran's presidential election
nigeria kidnapping explainer africa Asher pkg oneworld intl ldn vpx_00021802.png
nigeria kidnapping explainer africa Asher pkg oneworld intl ldn vpx_00021802.png
Now playing
02:20
'The stuff of nightmares': Breaking down Nigeria's kidnapping epidemic
screengrab china shenzhou 12 launch
CCTV
screengrab china shenzhou 12 launch
Now playing
01:59
See Chinese rocket launch to send astronauts to its space station
Putin praises biden Geneva summit Robertson lkl intl hnk vpx_00010025.png
Putin praises biden Geneva summit Robertson lkl intl hnk vpx_00010025.png
Now playing
02:09
Hear Putin offer rare praise for President Biden
Iran presidential election Pleitgen pkg intl hnk vpx_00021422.png
Iran presidential election Pleitgen pkg intl hnk vpx_00021422.png
Now playing
02:22
Hear from Iranian voters as they head to polls in presidential election
Host TV
Now playing
07:15
'What are you so afraid of?': Journalist presses Putin on political opposition
Russian President Vladimir Putin faces questions from reporters after his meeting with US President Joe Biden in Geneva, Switzerland.
Host TV
Russian President Vladimir Putin faces questions from reporters after his meeting with US President Joe Biden in Geneva, Switzerland.
Now playing
04:44
Putin faces question about cyberattacks against the US
CNN's Christiane Amanpour provides analysis following a summit between President Joe Biden and Russian President Vladimir Putin.
CNN
CNN's Christiane Amanpour provides analysis following a summit between President Joe Biden and Russian President Vladimir Putin.
Now playing
01:59
Amanpour: Biden did something very different than Trump
President Joe Biden meets with Russian President Vladimir Putin, Wednesday, June 16, 2021, at the 'Villa la Grange', in Geneva, Switzerland.
Patrick Semansky/AP
President Joe Biden meets with Russian President Vladimir Putin, Wednesday, June 16, 2021, at the 'Villa la Grange', in Geneva, Switzerland.
Now playing
02:55
Ward describes 'uncomfortable' photo op between Biden and Putin
biden putin summit us russia press pools clash collins sot vpx_00012417.png
biden putin summit us russia press pools clash collins sot vpx_00012417.png
Now playing
01:40
Collins: 'Combative exchanges' between Russian and US press corps
Pool
Now playing
02:49
See Biden and Putin shake hands as summit begins in Geneva
GAZA CITY, GAZA - JUNE 15: Flames are seen after an Israeli air strike hit Hamas targets in Gaza City, Gaza on June 15, 2021. (Photo by Ali Jadallah/Anadolu Agency via Getty Images)
Ali Jadallah/Anadolu Agency/Getty Images
GAZA CITY, GAZA - JUNE 15: Flames are seen after an Israeli air strike hit Hamas targets in Gaza City, Gaza on June 15, 2021. (Photo by Ali Jadallah/Anadolu Agency via Getty Images)
Now playing
03:58
Israel launches airstrikes in Gaza over incendiary balloons
China successfully launched the first module of its planned space station from the Wenchang launch site in the southern island of Hainan, according to the China National Space Administration.
CCTV
China successfully launched the first module of its planned space station from the Wenchang launch site in the southern island of Hainan, according to the China National Space Administration.
Now playing
01:04
See China's last rocket launch to send in space key component of its space station
CNN —  

The attack on the world’s largest oil processing plant early Saturday morning is a dramatic escalation in the confrontation between Iran and Saudi Arabia – even if the Iranians didn’t fire the drones or missiles responsible.

Several projectiles struck the Abqaiq plant, starting a series of fires that quickly took out nearly half Saudi’s oil production – 5% of the global daily output – and sparking fears about the security of the world’s oil supplies.

It’s unclear when Abqaiq, which is operated by Saudi giant Aramco, will be fully operational again.

A satellite image taken Saturday, September 14, 2019, shows thick black smoke rising from the Abqaiq oil processing facility in Saudi Arabia.
Planet Labs Inc via AP
A satellite image taken Saturday, September 14, 2019, shows thick black smoke rising from the Abqaiq oil processing facility in Saudi Arabia.

Houthi rebels in Yemen claimed the attack, saying that 10 drones had targeted Abqaiq, as well as the Khurais oilfield. But attacks of this scale and accuracy would represent a sudden and remarkable increase in Houthi capabilities, and neither the United States nor Saudi Arabia is buying the claim.

The United States swiftly discounted the Houthi claim. Late Saturday, Secretary of State Mike Pompeo tweeted: “Iran has now launched an unprecedented attack on the world’s energy supply.” And he added: “There is no evidence the attacks came from Yemen.”

In response Iranian Foreign Minister Javad Zarif accused Pompeo of engaging in deception. He wrote on Twitter: “Having failed at ‘max pressure’, @SecPompeo’s turning to ‘max deceit’ US & its clients are stuck in Yemen because of illusion that weapon superiority will lead to military victory. Blaming Iran won’t end disaster.”

But where did this attack originate and who was behind it?

The Houthis have sent dozens of drones and short-range ballistic missiles against Saudi Arabia in the past two years. Many have been intercepted by Saudi air defenses; others have fallen harmlessly. A very few have caused limited damage and casualties.

Houthi drones are based on Iranian models, themselves often developed from North Korean technology. They are mostly short-range, up to 186 miles (300 km). However, a UN experts’ panel reported in January on the deployment of longer-range drones “that would allow the Houthi forces to strike targets deep into Saudi Arabia and the United Arab Emirates.”

The UN panel said it had information that one had crashed within 18 miles (30 km) of Riyadh.

Even so, the maximum range of this system, dubbed the UAV-X, would be between 740 and 930 miles (1,200 and 1,500 km), depending on wind conditions. The distance from Houthi-held parts of Yemen to Abqaiq is about 800 miles (1,300 km).

A source with knowledge of the incident told CNN National Security Analyst Peter Bergen late Saturday that preliminary indications were the drones/missiles “did not originate from Yemen and likely originated from Iraq.” A second source in the Gulf region told CNN that while there was no proof yet, the indications were that the attack originated in southern Iraq.

Pro-Iranian militia are well-entrenched in southern Iraq, and the Quds Force, the Iranian Revolutionary Guards unit in charge of foreign operations, has a presence there. Earlier this year, some regional analysts assessed that a drone attack on a pumping station at Afif in northern Saudi Arabia originated in Iraq. But no hard evidence was produced.

The Iraqi government Sunday issued a statement rejecting reports “about its land being used to attack Saudi oil facilities.”

The Houthis themselves have suggested, without providing any evidence, that they had help from inside the kingdom for these latest attacks. Their spokesman Yahya Saree said the operation followed “an accurate intelligence operation and advance monitoring and cooperation of honorable people inside the kingdom.”

Analysts take that to mean elements of the restive Shia population in Saudi Arabia’s Eastern Province. Abqaiq lies between the predominantly Shia area of Qatif and Ahsa, which has a substantial minority Shia population. But they caution that it’s in the Houthis’ interests to try to stir internal tensions and it seems far-fetched that local people could have assisted such an attack.

The attack took out roughly half of Saudi Arabia's oil output.
Reuters
The attack took out roughly half of Saudi Arabia's oil output.

Wherever the attack originated and whoever pulled the trigger, these attacks are a step-change in what has already become a dangerous confrontation, with the sabotage of merchant shipping in the Gulf and the acute deterioration of the situation in Yemen, as well as several aerial attacks on Shia militia camps in Iraq in recent months.

While not confirming it was behind the attacks, Israeli Prime Minister Benjamin Netanyahu has said Israel is prepared to strike at pro-Iranian actors wherever they are considered a threat, including in Iraq.

No previous attack, since the Yemen conflict began four years ago, has interrupted oil supplies. This one has taken 5.7 million barrels a day off the market and demonstrated the vulnerability of the pumping heart of Saudi Arabia’s oil industry.

Saudi Arabia has invested heavily in advanced air defense systems. Ayham Kamal at the Eurasia Group says that the “critical problem for the kingdom is structural; most of Saudi Arabia’s air defense systems are designed to defend against traditional threats and are ill-equipped to tackle asymmetrical aerial threats such as drones.”

That vulnerability is enhanced when so many essential parts of the infrastructure – “storage, processing, and compressor trains – are located within a small area,” he adds.

The attacks have drawn in the international community, with the US declaring that it is ready to open its Strategic Petroleum Reserve if necessary, and President Donald Trump calling Saudi Crown Prince Mohammed bin Salman.

At present, there is plentiful oil on the market. OPEC and its producing ally Russia have cut production this year to support prices. But Saudi Arabia is normally the organization’s “swing producer” with the ability to reduce or increase the flow as required. That ability is crimped for now.

Much depends on the damage reports, and what “work-arounds” might be possible to restore full production and soothe markets’ nerves. “The most critical elements of Saudi Arabia’s oil infrastructure include several redundancies,” Kamal says.

How Saudi Arabia will respond in other ways – such as redoubling its military campaign against the Houthis in Yemen – is yet to be seen.

CNN’s Aqeel Najim and Sara Mazloumsaki contributed to this report.