Russia has closed off the Kerch Strait – the strait connecting the Black Sea and Azov Sea – for non-military ships in retaliation to what the Kremlin calls trespassing into Russia’s territorial waters by three Ukrainian Navy boats, according to Alexey Volkov, general director of Russian state enterprise Crimean Sea Ports, Russian news agency TASS reported on Nov. 25.

Volkov said that the strait has been closed “for security reasons.”