Commercial shipping through the Strait of Hormuz has contracted sharply, with the number of daily transits falling to just six commodity carriers on Sunday, according to ship-tracking data from Kpler. That marks the lowest level since mid-June, before a fragile US-Iran memorandum of understanding briefly restored confidence. Over the past several days, so-called “dark crossings” — vessels navigating with their Automatic Identification System transponders switched off — have outnumbered observable passages, as shipowners seek to avoid being targeted in the escalating exchange of strikes between Washington and Tehran.

Iranian authorities have declared that the strait is closed to unauthorised traffic and that vessels must obtain permission from an Iranian body before transiting. The Islamic Revolutionary Guard Corps claimed on Sunday to have intercepted two ships it said were using an “illegal route,” and Tehran has stated it will review permissions only after “stability and calm” are restored. By contrast, US Central Command insists the waterway remains open to all commercial shipping through international lanes, and President Donald Trump has vowed to charge a levy on cargo passing through Hormuz to fund the American security presence. Washington has also reinstated a blockade on Iranian vessels, lifted only weeks ago under the earlier understanding.

The practical effect is a bifurcation of risk. The southern, Omani corridor — historically the main peacetime route and backed by the US — has seen publicly tracked transits effectively cease since Wednesday, after a series of Iranian attacks on ships using that passage, including vessels that had already disabled their transponders. The northern route, designated by Iran, recorded a limited number of crossings through Saturday, but shipowners using it face potential US sanctions and additional fees demanded by Tehran. Maritime intelligence analysts note that some clients are still crossing the southern corridor with direct US naval support, such as counter-projectile fire and timing advice, though the International Maritime Organization has warned the area is unsafe because of sea mines.

The disruption threatens a chokepoint through which roughly one-fifth of global oil consumption passes. Brent crude prices rose 4 percent on Monday to near $80 a barrel, and Asian equity markets fell. Iranian military officials have said US intervention has “seriously undermined” energy supplies, while the US has conducted further precision strikes on Iranian targets to degrade the ability to interfere with navigation. With both sides issuing irreconcilable claims over control of the waterway and no diplomatic track immediately visible, shipping companies are left navigating a narrow and perilous set of choices, often in radio silence.