In November 2018, Russia confiscated three Ukrainian ships, including the crew, 22 marines and two members of the Ukrainian secret service. These ships had entered Russian waters in the Kerch Strait without registration. After ignoring several warnings from the Russian coastguard, the Ukrainian ships were finally seized by Russian border guards and the FSB.
On 25 November 2018, border patrol boats belonging to Russia’s FSB security service seized two small Ukrainian armoured artillery vessels and their crews after shooting at them, wounding several Ukrainian servicemen. Russia argued that they were in Russian waters. However, a bilateral treaty between Russia and Ukraine, signed in 2003 and ratified by Russia in 2004, governs the use of the Kerch Strait and the Sea of Azov, which the agreement considers being the “internal waters” of both Russia and Ukraine.
On May 25, 2019, the United Nations Tribunal for the Law of the Sea ordered Russia to immediately release Ukrainian sailors and allow them to return to Ukraine. The EU has also urged Russia to release the captured crew.