Iran has moved to assert its control over the Strait of Hormuz, declaring that ships can't cross without its permission and setting the stage for future tolling arrangements.
The country's Persian Gulf Strait Authority said vessels will have to secure a mandatory insurance policy, currently free but potentially involving charges in the future.
Ships must follow a prescribed route along Iran's coast, with alternatives prohibited, and have been told to submit requests to the PGSA for passage permits.
The move has sparked concerns among shippers and producers that Iran will seek to toll the strait in the future, breaking with international maritime law and setting a dangerous precedent.