The US military has released a video which it says shows Iranian special forces removing an unexploded mine from the side of an oil tanker damaged in an attack in the Gulf of Oman on Thursday.
The US also released images of the Japanese tanker apparently showing the unexploded mine before it was removed.
A Norwegian tanker in the gulf also reported being hit by three blasts.
The US accused Iran of being behind the attacks. Iran said it “categorically” rejected the allegation.
The blasts came a month after four oil tankers were damaged in an attack off the coast of the United Arab Emirates. The US blamed Iran for that attack, but did not produce evidence. Iran also denied those accusations.
Tensions between the US and Iran have escalated significantly since US President Donald Trump took office in 2017. He abandoned a nuclear deal that was brokered by the Obama administration and significantly tightened sanctions on Iran.
On Friday, Mr Trump repeated the US assertion that Iran was behind the incident in an interview with Fox News.
He also said it was unlikely that Iran could close the Strait of Hormuz – a vital shipping lane through which a third of the world’s seaborne oil passes every year – but if it did, the strait would not remain closed “for long”.
Asked how to stop Iran, Mr Trump said: “We’ll see.”
Oil prices jumped as much as 4 per cent after Thursday’s incident.
According to the US account of events, US naval forces in the region received distress calls from the Norwegian-owned Front Altair at 06:12 (02:12 GMT) and from the Japanese-owned Kokuka Courageous at 07:00, following explosions, and moved towards the area.
It said the USS Bainbridge observed Iranian naval boats operating in the area in the hours after the explosions, and later removing the unexploded mine from the side of the Kokuka Courageous.
The crews of both vessels were evacuated to other ships nearby. Both Iran and the US later released pictures showing rescued crew members on board their vessels.
BSM Ship Management, which manages the Kokuka Courageous, said the ship’s crew abandoned the ship after observing a fire and an unexploded mine. –BBC