Kerch Strait incident

An international incident occurred on 25 November 2018 when the Russian Federal Security Service coast guard fired upon and captured three Ukrainian Navy vessels attempting to pass from the Black Sea into the Sea of Azov through the Kerch Strait on their way to the port of Mariupol. In 2014, Russia had annexed the nearby Crimean Peninsula, which is dominantly internationally recognised as Ukrainian territory. It later constructed the Crimean Bridge across the strait. Under a 2003 treaty, the strait and the Azov Sea are intended to be the shared territorial waters of both countries, and freely accessible.
As the flotilla, which consisted of two gunboats and a tugboat, approached the Kerch Strait, the Russian coast guard said they repeatedly asked the Ukrainian vessels to leave what they referred to as "Russian territorial waters". They said that the vessels had not followed the formal procedure for passage through the strait, that the Ukrainian ships had been manoeuvring dangerously, and that they were not responding to radio communications. Ukraine said that it had given advance notice to the Russians that the vessels would be moving through the strait, that the ships had made radio contact with the Russians, but received no response, and cited the 2003 treaty against the assertion that the ships had entered Russian territorial waters. The Russians tried to halt the Ukrainian ships, but they continued moving in the direction of the bridge. As they neared the bridge, the Russians authorities placed a large cargo ship under it, blocking their passage into the Azov Sea. The Ukrainian ships remained moored in the strait for eight hours, before turning back to return to port in Odessa. The Russian coast guard pursued them as they left the area, and later fired upon and seized the vessels in international waters off the coast of Crimea. Three Ukrainian crew members were injured in the clash, and all twenty-four Ukrainian sailors from the captured ships were detained by Russia.

Wikipedia