IRAN is being accused of masterminding attacks that have crippled the world's largest oil plant, using cruise missiles and swarms of drones.
The massive strike on its archenemy Saudi Arabia is being dubbed a “Pearl Harbour” which could spark a massive war in the Middle East.
Tehran denies involvement in the incident, which has caused oil prices to rocket by 20 per cent — the biggest ever increase.
But Yemen's Iran-aligned Houthi group has already claimed responsibility and promised more attacks.
Up to 20 drones were thought to be involved, with some of the unmanned craft powered by jet engines.
And US officials said today cruise missiles were also used.
A source speaking on condition of anonymity said: "There's no doubt that Iran is responsible for this.
“No matter how you slice it, there's no escaping it. There's no other candidate.”
Randy Larsen, a former professor and department head at the US military's National War College, told Bloomberg: "This has the potential to be as significant as Pearl Harbour.”
The sheer scale of the attack may spark war between Saudi Arabia and Iran.
Both nations have been enemies for decades and are fighting a number of proxy wars, including in Yemen where Saudi forces have been fighting against the Iranian backed Houthis for four years.
This has the potential to be as significant as Pearl Harbour
Military expert Randy Larsen
Overall tension in the oil-producing Gulf region has dramatically escalated this year after Trump imposed severe sanctions on Iran aimed at halting its oil exports altogether in a bid to shut down its nuclear weapons programme.
In June Iran's ruthless Revolutionary Guard was blamed for attacks on two oil tankers in the Gulf of Oman.
Iran seized the British flagged Stena Impero on July 19 shortly after the UK detained a vessel in Gibraltar that was allegedly carrying Iranian crude oil to Syria.
The drone attack has underscored fears raised by US security experts about the rapid evolution of unmanned aircraft, which are relatively cheap to make and are effective.
Notably the drones were able to pierce Saudi Arabia high tech air defences.
But cruise missiles were said to have been used too, which underlines huge advances in Iranian weapons technology.
Iran's elite Revolutionary Guard force said last night it was prepared for a "full-scale war".
The commander of the Islamic Revolutionary Guard Corps' aerospace arm, Amirali Hajizadeh, bragged that Iran's missiles could hit US bases and ships within a range of 1,240 miles.
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Meanwhile US President Donald Trump tweeted his military was “locked and loaded”.
War between Iran and Saudi Arabia is likely be vicious and cause major disruption to global fuel supplies.
The Saudi attack alone caused the biggest jump in prices ever.
Saul Kavonic, an energy analyst at Credit Suisse Group, said: “We have never seen a supply disruption and price response like this in the oil market.
“Political risk premium are now back on the oil market agenda.”
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