On 25 November 2018, three ships of the Ukrainian Navy deliberately violated Russian territorial waters during their passage from the Black Sea to the Sea of Azov.
When the three warships reached Russian territorial waters, they received a warning from the security forces of the Russian Navy and were asked to change course. However, they ignored the calls, triggering a chase in the Kerch Strait, in which shots were fired and three Ukrainian marines were lightly wounded. As a result, the Ukrainian warships were detained and brought to Kerch.
In this incident, Russia deliberately blocked the Kerch Strait in order to prevent the passage of a naval group of the Ukrainian Navy.
On 25 November 2018, three Ukrainian war ships were moving “in accordance with the provisions of all effective multilateral and bilateral international treaties and navigation rules”. The Ukrainian war ships were seized and their crews were detained, despite the fact that the UN Convention on the Law of the Sea (UNCLOS) states that “all ships, including foreign warships, enjoy the right of “innocent passage” within another state’s territorial sea under international law.”
On 25 November, border patrol boats belonging to Russia’s FSB security service seized the two small Ukrainian armoured artillery vessels and their whole crews after shooting at them, wounding several Ukrainian servicemen.
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 in the treaty is considered to be the “internal waters” of both Russia and Ukraine.