A Russian-administered court in Ukraine's Crimean Peninsula ruled on February 16 to detain four Ukrainian fisherman for 10 days as civil punishment for "illegally fishing" in the Sea of Azov where they were detained and had their boat impounded the previous day.
Russia's Federal Security Service (FSB) border guard force said it apprehended the four Ukrainians off the coast of Crimea and accused them of "violating the rules for catching aquatic biological resources."
The fishermen didn't have documents on their person and the catch on board the vessel was illegal, said Larisa Opanasyuk, the human rights ombudswoman on the Russian-occupied peninsula.
A 2003 Russia-Ukraine treaty stipulates unimpeded access to the Kerch Strait and Sea of Azov.
Ukraine's presidential representative in annexed Crimea based in the southern Kherson region said it was the monitoring the situation with the four fishermen.
On November 25, 2018, Russian border guards attacked, intercepted, and seized three Ukrainian Navy boats off Crimea, taking 24 crew members prisoner.
The following November, Russia returned the severely damaged Ukrainian vessels and a UN tribunal had ordered Russia to immediately release the crew members and ships in May.
The sailors were freed after 10 months in a landmark prisoner exchange in September.
Russia invaded Crimea in early 2014 and has controlled the peninsula ever since, triggering Western sanctions that are still in place.