Iran has released video purporting to show the seizure of a US-bound, Marshall Islands-flagged oil tanker.
In footage aired by Iranian state television, masked commandos can be seen descending from a helicopter on to the Advantage Sweet oil tanker.
The tanker was on its way from Kuwait to Houston, Texas, on Thursday.
Iran's military said the boat was taken into custody after an incident with an Iranian vessel which injured several and left two missing.
Turkish firm Advantage Tankers, which manages the vessel, issued a statement acknowledging the Advantage Sweet was “being escorted by the Iranian navy to a port on the basis of an international dispute”.
All of the ship's 24 crew members are Indian. Indian authorities have yet to comment on the seizure.
“The safety and welfare of our valued crew members is our number one priority,” the firm said. “Similar experiences show that crew members of vessels taken under such circumstances are in no danger.”
The US Navy's 5th Fleet has said the Iranian seizure was at least the fifth commercial vessel taken by Tehran in the past two years.
US naval command said the Islamic Revolutionary Guard Corps' actions are “contrary to international law and disruptive to regional security and stability” and urged Iran to “immediately release” the vessel.
Thursday's seizure was the latest disruptive incident in the sensitive waters of the Arabian Gulf, through which about a third of the world's seaborne oil passes.
Such incidents have escalated since 2018, when the US withdrew from a multinational accord meant to limit Iran's nuclear programme in return for sanctions relief. Marathon talks to restart the accord have stalled.
The latest seizure came days after western nations toughened sanctions on the IRGC.