Iran's Islamic Revolutionary Guard Corps (IRGC) reported fires aboard several oil tankers in the region around the Strait of Hormuz.
Four tankers were attacked while transferring oil to other vessels and three other ships struck mines overnight, the IRGC said in a statement on Thursday.
The claims could not be independently verified.
The IRGC again described passage through the strait as illegal and threatened to expand its attacks against the United States.
Iran's armed forces have intensified their attacks on shipping in the Strait of Hormuz in recent weeks.
For several months, the US Navy has been escorting civilian vessels along the Omani coast in an effort to restore trade in oil and liquefied natural gas.
After passing through this route, tankers usually transfer their cargo to other ships waiting nearby.
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