On November 25, 2018, three small ships of Ukrainian Navy, two artillery boats and a tugboat, tried to sail through the controlled by Russia Kerch Strait. The ships were heading to the Ukrainian ports in the Sea of Azov. In the morning Russian frontier guard ships rammed the Ukrainian tugboat and severely damaged it. Ukrainian ships were waiting for the passage for a couple of hours. Then they decided to leave the Kerch Bay and return to Odessa. Russian vessels started to chase them and opened fire on the Ukrainian ships. It all happened in international waters. The Russian FSB special forces have boarded Ukrainian ships, capturing 24 seamen - as it turned out, six of them were injured as a result of shelling. As a consequence of the Russian attack, Ukrainian authorities decided to impose martial law.