Fars Plus, an outlet associated with Iran’s semi-official Fars News Agency, has published two voice notes attributed to the Islamic Revolutionary Guard Corps (IRGC).

In them, warnings are issued in Persian and English to vessels in the Gulf, the Strait of Hormuz and the Sea of Oman saying the Strait "remains closed".

I've listened in and this is what the messages say:

"This is a serious warning from the naval forces of the IRGC. The Strait of Hormuz remains closed, and passage through it without the permission of the Islamic Republic of Iran and outside the designated route is prohibited.

"If any vessel passes without permission at longitude 56°00′ East in the Persian Gulf and latitude 25°40′ North in the Sea of Oman, it will be struck and destroyed."

-BBC