Four Iranian-flagged oil tankers passed through the Strait of Hormuz on Monday, a first since April 15 and the US blockade of Iranian ports, AFP reports citing maritime tracking firm Kpler.

Data from the firm detected the passage of the Hilda I, the Amber, the Silvia 1, and the Happiness I, which were carrying a total of 7 million barrels of oil.

They all loaded their cargo in mid-April on Kharg Island, the country’s main oil terminal, through which 90 per cent of the Islamic republic’s crude oil normally transits.

The ships crossed the strait on Monday with their AIS (automatic identification system) transponders turned off. Kpler relies primarily on satellite imagery to track ships transporting raw materials.