Saudi Arabia said Saturday it was ready to respond to drone attacks claimed by Iran-aligned Yemeni rebels on two major oil facilities, which severely disrupted production as Washington blamed Tehran for the strike.
The strikes sparked fires at the state-owned Aramco oil plants and prompted furious condemnation from the top US diplomat who blamed Tehran for the strike.
Huge palls of smoke rose into the sky after the pre-dawn attacks on Abqaiq and Khurais, two key Aramco facilities in eastern Saudi Arabia as the giant prepares for a much-anticipated stock listing.
The drones triggered multiple explosions, forcing state-owned Aramco to temporarily suspend production at the two facilities, interrupting about half of the company's total output, Energy Minister Prince Abdulaziz bin Salman said.
The Iran-linked Huthi rebels said they launched "a large-scale operation involving 10 drones" on the facilities, the group's Al-Masirah television reported.
However US Secretary of State Mike Pompeo blamed Tehran for the attack, saying there was no evidence it was launched from Yemen.
"Iran has now launched an unprecedented attack on the world's energy supply," Pompeo said on Twitter.
"The United States will work with our partners and allies to ensure that energy markets remain well supplied and Iran is held accountable for its aggression," the top US diplomat added.
Following a phone call between US President Donald Trump and Saudi Crown Prince Mohammed bin Salman, the White House condemned the attacks on "infrastructure vital to the global economy".
Prince Mohammed had earlier issued a statement saying the kingdom was "willing and able" to respond to this "terrorist aggression", according to Saudi state media.
Washington's condemnation of Tehran throws into doubt expectations that Trump is trying to arrange a meeting with Iranian President Hassan Rouhani at the upcoming United Nations assembly.
- Crude output halved -
Saudi interior ministry spokesman Mansour al-Turki told AFP there were no casualties in the attacks in the kingdom's Eastern Province.
But the full extent of the damage was not immediately clear as reporters were not allowed near the plants where Saudi authorities swiftly beefed up security.
The attacks on the Abqaiq plant -- Aramco's largest oil processing facility -- and nearby Khurais, which hosts a massive oil field "resulted in production suspension of 5.7 million barrels of crude oil per day", the company said.
Aramco CEO Amin Nasser said work was under way to restore production and a progress update would be provided in the next two days.
Explosions at the plant also led to a production halt of an estimated two billion cubic feet of gas per day, Prince Abdulaziz said.
The UN's Yemen envoy Martin Griffiths said he was "extremely concerned" over the latest attacks, which also drew swift condemnation from Riyadh's Gulf allies, the United Arab Emirates, Bahrain and Kuwait.
In recent months, the Huthi rebels have carried out a spate of cross-border missile and drone attacks targeting Saudi air bases and other facilities in what they say is retaliation for a long-running Riyadh-led bombing campaign on rebel-held areas in Yemen.
Last month, an attack claimed by Huthi rebels sparked a fire at Aramco's Shaybah natural gas liquefaction facility -- close to the Emirati border -- but no casualties were reported by the company.
Rebel drones also targeted two oil pumping stations on Saudi Arabia's key east-west pipeline in May, shutting it down for several days.
Growing rebel attacks underscore how Saudi infrastructure, including oil installations, are increasingly vulnerable to the Huthis' steadily advancing weaponry -- from ballistic missiles to unmanned drones.
- Aramco IPO -
The Abqaiq plant, which Aramco says plays a "pivotal role" in its operations, has been targeted by militants in the past.
In an attack claimed by Al-Qaeda in February 2006, suicide bombers with explosive-laden vehicles attempted to penetrate the processing plant, killing two security guards.
The two bombers also died in the attack, which failed to breach the compound, authorities reported at the time.
The United States and Saudi Arabia have blamed Tehran for multiple attacks on tankers in the Gulf, and in June, Trump called off air strikes against Iran at the last minute after it downed a US drone.
The latest attacks come as Saudi Arabia accelerates preparations for a much-anticipated initial public offering of Aramco, the world's most profitable company.
The mammoth IPO forms the cornerstone of a reform programme envisaged by the powerful crown prince to wean the Saudi economy off its reliance on oil.
Aramco is ready for a two-stage stock market debut including an international listing "very soon", its CEO Amin Nasser told reporters on Tuesday.