US naval blockade leaves Iranian oil with nowhere to go

Exacerbating wider market tightness

"At this stage, we estimate that around four million barrels of Iranian crude has successfully moved out of the Gulf of Oman. We are not currently able to confirm whether any of those vessels have since been interdicted," it said in an email to Reuters.

The loss of Iranian supply adds to wider market tightness as the war has effectively closed the Straight of Hormuz, curtailing oil exports from Saudi Arabia, the UAE, Kuwait and Iraq and sending prices higher, something the US has sought to avoid.

Last month, the US granted Tehran an unexpected temporary sanctions waiver on energy exports to allow prices to cool.

Benchmark Brent crude oil futures have jumped by about $50 a barrel since the Iran war began on February 28, raising prices of gasoline, diesel and jet fuel.

The International Energy Agency has called it the world's largest oil output disruption.