As Iran-backed Yemeni rebels claimed responsibility for an attack on one of the world's largest oil processing facilities in Saudi Arabia, Secretary of State Mike Pompeo on Saturday blamed Tehran directly.
"Amid all the calls for de-escalation, Iran has now launched an unprecedented attack on the world’s energy supply," he said on Twitter. "There is no evidence the attacks came from Yemen."
Drones claimed by Yemen's Houthi rebels struck the oil processing facility in Saudi Arabia and a major oilfield operated by Saudi Aramco early Saturday, sparking a huge fire at a processor crucial to global energy supplies.
The kingdom's official news outlet, the Saudi Press Agency, said Saturday that no workers were injured. It said the attack would reduce production at Khurais and Abqaiq facilities by half, but that output would be buoyed by tapping reserves.
Liquified natural gas and ethane production in the Kingdom was halved as a result of the explosions, the agency said.
"We call on all nations to publicly and unequivocally condemn Iran's attacks," Pompeo said on Twitter Saturday. "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."
A senior Trump administration official told NBC News that the attack, involving supplies vital to the global economy, "is one of the most provocative in a 40-year pattern of escalatory violence" from Tehran.
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It "completely contradicts the regime's hypocritical calls for diplomacy," the official said.
The U.S. envoy to Saudi Arabia also condemned the attacks Saturday.
"These attacks against critical infrastructure endanger civilians, are unacceptable, and sooner or later will result in innocent lives being lost," the U.S. mission quoted Ambassador John Abizaid as saying.
The office of the U.N. Special Envoy for Yemen said in a statement that it was "extremely concerned" about the attacks.
"The Special Envoy urges all parties to prevent such further incidents, which pose a serious threat to regional security, complicate the already fragile situation and jeopardize UN-led political process,” it said.
Saudi state television aired a segment with a correspondent in Buqyaq as smoke from the blazes clearly rose behind. That smoke also was visible from space.
The fires began after the sites were "targeted by drones," the Interior Ministry said in a statement carried by the state-run Saudi Press Agency. It did not directly blame anyone for the attack and said an investigation was underway.
In a short address aired by the Houthi's Al-Masirah satellite news channel, military spokesman Yahia Sarie said the rebels launched 10 drones in their coordinated attack on the sites. He warned attacks by the rebels would only get worse if the war continues.
"The only option for the Saudi government is to stop attacking us," Sarie said.
Saudi Aramco, the state-owned oil giant, did not immediately respond to questions from The Associated Press. The kingdom hopes soon to offer a sliver of the company in an initial public offering.
Saudi Aramco describes its Abqaiq oil processing facility in Buqyaq, some 205 miles northeast of the Saudi capital Riyadh, as "the largest crude oil stabilization plant in the world."
The facility processes sour crude oil into sweet crude, then later transports onto transshipment points on the Persian Gulf and the Red Sea. Estimates suggest it can process up to 7 million barrels of crude oil a day.
The plant has been targeted in the past by militants.
The Khurais oil field is believed to produce over 1 million barrels of crude oil a day. It has estimated reserves of over 20 billion barrels of oil, according to Aramco.
There was no immediate impact on global oil prices as markets were closed for the weekend across the world.
The war has become the world's worst humanitarian crisis.
The violence has pushed Yemen to the brink of famine and killed more than 90,000 people since 2015, according to the U.S.-based Armed Conflict Location & Event Data Project, or ACLED, which tracks the conflict.
Since the start of the Saudi-led war, Houthi rebels have been using drones in combat.
The rebels have flown drones into the radar arrays of Saudi Arabia's Patriot missile batteries, according to Conflict Armament Research, disabling them and allowing the Houthis to fire ballistic missiles into the kingdom unchallenged.
U.N. investigators said the Houthis' new UAV-X drone, found in recent months, likely has a range of up to 930 miles. That puts the far reaches of Saudi Arabia in range.
Dennis Romero writes for NBC News and is based in Los Angeles.
Reuters, Kelly O'Donnell and Andrea Mitchell contributed.