Iran's foreign ministry dismissed as "baseless" Friday morning US accusations it was behind twin attacks on tankers in the Gulf of Oman, adding Washington was trying to "sabotage diplomacy".

The US had "immediately jumped to make allegations against Iran --(without) a shred of factual or circumstantial evidence," Foreign Minister Mohammad Javad Zarif said in a tweet.

Zarif claimed that the US accusations showed that Washington was moving from "talking about diplomacy" to what he described as "Plan B" of "sabotaging diplomacy."   

US Secretary of State Mike Pompeo accused Iran of being behind Thursday's attacks which left at least one of the tankers ablaze off the Iranian coast, while the crews had to abandon ship.

"It is the assessment of the United States that the Islamic Republic of Iran is responsible for the attacks," Pompeo told reporters.

Iranian foreign ministry spokesman Abbas Mousavi retorted that Tehran had come to "help" the ships in distress and "saved" their crew as quickly as possible, in a statement on his Telegram channel.

Pompeo said there was strong evidence of Iran's culpability "based on the intelligence, the weapons used, the level expertise needed to execute the operation" and the US assumption that only Iran in the region has the ability to undertake such an operation.

"Apparently for Mr. Pompeo and other American authorities accusing Iran is the easiest thing to do," said Mousavi, insisting Iran was upholding the burden of securing the strategic Strait of Hormuz.

Iran's state-owned English-language TV channel Press TV cast doubt on the "evidence" presented by Washington in support of its accusation against Tehran.

US Central Command said it saw an Iranian patrol boat removing an "unexploded limpet mine" from the hull of the Japanese-owned tanker Kokuka Courageous and published grainy video.

Press TV complained that the video missed the moment where the crew of the Iranian boat reportedly removed the alleged mine.

"Facts: (the Guards Corps) was the closest force near the incident site. Iran was the first to rush to the scene to save the crew members," Press TV said in a tweet.

"Do you think Pentagon footage proves Washington's claim of Iran's 'involvement'?" it added.

*This story was edited by Ahram Online