The three ships were sailing off the coast of Crimea, which was annexed by Russia in 2014, when they were seized. Russians opened fire, before its special forces stormed the vessels. Some Ukrainians were injured.

 Moscow accused the Ukrainian ships of illegally entering its waters, after the FSB had temporarily closed an area of water for shipping. Kiev called it a flagrant violation of international law, because the Black Sea is free for shipping, and annexed Crimea belongs to Ukraine.

Ukraine also cited a 2003 Russia-Ukraine treaty on unimpeded access to the Kerch Strait and Sea of Azov. It said it had informed the Russians in advance of its plan to move its ships through the sea to Mariupol – a claim denied by Russia.

In recent weeks, two Ukrainian vessels passed through the Kerch Strait without incident.