Some vessels managed to slip through the United States’ naval blockade of Iranian ports and the Strait of Hormuz, maritime data showed on Thursday.

Ship-tracking data cited by The Washington Post showed at least 15 cargo vessels had transited the strait since the blockade was imposed earlier this week.

Nine ships exited the Persian Gulf while six entered, including several that had called at Iranian ports.

One vessel, the Argo Maris, departed Bandar Abbas carrying bitumen bound for Oman, highlighting that limited trade flows persisted despite the US interdiction effort.

Before the outbreak of hostilities, roughly 130 vessels transited the strait daily, making the current figures a sharp decline but not a complete halt.

American forces have also compelled compliance from several ships, with at least nine vessels reportedly turned back within the first 48 hours of the blockade enforcement.

The New York Post reported that a sanctioned Chinese-linked tanker, the Rich Starry, managed to cross the strait before being forced to reverse course and return to Iranian waters.

The incident, based on tracking data, illustrated how US naval patrols were tightening control, particularly on the eastern approaches to Hormuz in the Gulf of Oman.

At least five vessels attempting to exit the region have been stopped or redirected, suggesting that while the blockade is not airtight, it is increasingly effective in disrupting Iranian oil exports.

At the same time, Iran has reportedly deterred broader traffic by threatening vessels that do not comply with its demands, compounding the disruption in one of the world’s most critical energy corridors.

The economic pressure campaign is being reinforced through sanctions.

According to Agence France-Presse, Washington has announced a new round of penalties targeting Iran’s oil transport network, including companies and ships linked to the Shamkhani family, a powerful entity within Iran’s petroleum logistics system.

US Treasury Secretary Scott Bessent said the measures are part of an “Economic Fury” strategy designed to limit Iran’s ability to generate revenue as it seeks to leverage control over the strait.

The sanctions also target individuals and firms accused of circumventing earlier restrictions through complex shipping and financial arrangements.

Iran, for its part, has effectively shut down most traffic through the Strait of Hormuz in retaliation for US and Israeli military operations, transforming the waterway into a flashpoint with global economic implications.

The strait typically handles about a fifth of the world’s oil supply.