Commodity vessel transits through the Strait of Hormuz dwindled to just three ships on Wednesday, down from 12 a day earlier and well below the 10-day average of about 17, preliminary ship-tracking data showed on Thursday.
The figures exclude any vessels that might have passed through the waterway with their Automatic Identification System transponders turned off to avoid detection.
Of the three vessels, an empty Supramax dry bulk ship entered the strait via the Iranian route, while an empty petroleum product tanker entered through a dark route, shipping data from Kpler showed at 0445 GMT.
A Panamax tanker exited the waterway using a dark route, the data showed.
Vessel traffic dropped this week as war in the Gulf intensified. Saudi Arabian warplanes pounded Yemen and Houthi fighters launched drones and missiles at Saudi cities.
The Iran-backed Houthis' rapid advance in Yemen along the Red Sea coast, attacks on Saudi Arabia and damage to the kingdom's East-West oil pipeline have widened Tehran's reach in the conflict and raised risks to global oil supplies.
In the Red Sea, vessel crossings through the Bab el-Mandeb Strait eased to 21 on Wednesday, compared with 24 vessels a day earlier.
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