Iranian Revolutionary Guard gunboats opened fire on a tanker passing through the Strait of Hormuz on Saturday, according to the British military, in an incident that follows Tehran’s announcement that it has reimposed restrictions on the critical shipping route.

The United Kingdom Maritime Trade Operations center said the vessel and its crew were unharmed, though it did not disclose the tanker’s identity or destination.

Mohammad-Bagher Qalibaf, speaker of Iran’s Parliament, said on Friday that Iran would again close the Strait of Hormuz as a result of the U.S. blockade of Iranian ports. 

Iran said it was reinstating controls over traffic in the strait. Throughout the seven-week conflict, Tehran has largely barred vessels from transiting the waterway unless they receive explicit authorization.