At least four vessels tracked from Iranian ports appear to have crossed a US blockade line in the Gulf of Oman, analysis of ship-tracking data suggests.

The US blockade of ships using Iranian ports has come into force but several Iran-linked tankers have passed through the strait of Hormuz since it began. Lucy Hough speaks to the…

Analysts say that Iran has already moved vast quantities of its oil offshore and a full blockade would be complex to implement