Iran vows response to 'cowardly' missile attack on tanker off arch-rival Saudi coast

Ali Shamkhani, secretary of the Supreme National Security Council, said clues had been uncovered as to who was behind what he called a "missile attack" on the Sabiti tanker.

"Maritime piracy and wickedness in international waterways... will not be left unanswered," he said, quoted by ISNA.

"By reviewing the available video and gathered intelligence evidence, the primary clues to the dangerous adventure of attacking the Iranian oil tanker in the Red Sea have been uncovered," he added.

Shamkhani warned of "disturbing risks" for the global economy as a result of insecurity in international waterways.

The National Iranian Tanker Company, which owns the Sabiti, said its hull was hit by two separate explosions on Friday off the Saudi port of Jeddah,

But the state-owned company denied reports the attack had originated from Saudi soil.

The attack caused oil to spill from the tanker into the Red Sea, the NITC said, before it was eventually controlled and the vessel began slowly moving back towards Gulf waters.

According to the latest data from shipping monitors Marine Traffic, the Sabiti was still in the Red Sea about 400 kilometres (250 miles) south of Jeddah.

Read more: After the Aramco attack: A Middle East one step closer to its '1914 moment'

The incident comes after a spate of still unexplained attacks on shipping in and around the vital seaway to the Gulf involving Iran and Western powers, as well as drone attacks on Saudi oil installations.

Washington accused Tehran of attacking the vessels with mines and to be behind the drone assault, something it strongly denied.

In a statement, Iran's government spokesman Ali Rabiei called Friday's attack "cowardly" and said Tehran would give a "proportionate response" following investigations.

"The question now is, those who accused Iran of disrupting free maritime transport in the Persian Gulf and the attack on Aramco installations with no proof, are they ready to once again defend the principles of free maritime transportation in international waters and condemn such an attack on an Iranian ship?" he said.

Tehran did not blame arch-rival Riyadh for the attack on its tanker, while US defence officials said they were still looking into it and had no immediate explanation.

'14,000 more US troops' 

However, shortly after the attack, the US confirmed it will send fighter jets and additional air defences to Saudi Arabia to defend the kingdom against Iran amid heightened tensions between the two Middle Eastern adversaries.

US Defence Secretary Mark Esper said that two fighter squadrons and additional missile defence batteries were being sent to Saudi Arabia.

"Taken together with other deployments this constitutes an additional 3,000 forces that have been extended or authorised within the last month," the Pentagon said in a statement.

Esper said he had spoken with Saudi Crown Prince Mohammad bin Salman on Friday to discuss adding US firepower to the oil giant's defences against Iranian attacks.

Esper said that since May the United States has increased its 70,000-strong presence in the Middle East by 14,000 personnel, most of those deployed to the Gulf region in response to Iran's actions.

"The US military has on alert additional army, navy, marine and air force units to quickly provide increased capability in the region if necessary," he said Friday.

He also urged US allies in Europe to follow America's lead with their own defensive assets "for regional stability."

The deployments authorised Friday include two additional fighter squadrons, and supporting personnel, along with additional Patriot and THAAD missile defence batteries. 

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