The Parliamentary Assembly of Council of Europe called on Russia to release the 24 Ukrainian sailors who were captured in November 2018 after they violated the Russian border.
This is a recurring pro-Kremlin disinformation narrative about the November 2018 Kerch incident. On 25 November 2018, border patrol boats belonging to Russia’s FSB security service seized two small Ukrainian armoured artillery vessels and a tug boat and their crews after shooting at them, wounding several Ukrainian servicemen and arresting 24. Russia argued that they were in Russian waters. The EU has urged Russia to release the captured crew.
However, the Kerch Strait and the Sea of Azov, as addressed by the 2003 bilateral agreement between Ukraine and Russia are defined as the internal waters of both Russia and Ukraine. The agreement gives both parties the power to inspect suspicious vessels. Furthermore, both the 2003 bilateral agreement and UN Convention on the Law of the Sea provide for the freedom of navigation.
More cases about the Kerch Strait incident are available here.