Iran reportedly used small boats to mine the Strait of Hormuz in March, starting shortly after the US and Israel began bombing Iran on February 28.
Individual routes through the strait have been left free of mines, but Iran has demanded that a toll be paid to pass through.
Normally, a fifth of the world's oil and gas supplies pass through the Strait of Hormuz. The supply disruptions have pushed up the price of crude oil by almost 50 percent compared to prices before the war with Iran.
