Ukraine’s Security Service (SBU) says it has seized a Russian tanker that Moscow allegedly used to block three Ukrainian naval vessels before detaining them and 24 Ukrainian sailors in November near Crimea.
The SBU said in a statement posted on its Facebook page on July 25 that an investigation revealed that Russia's Federal Security Service and Border Guard Service used a tanker named Neyma to "illegally block the movement of the Ukrainian naval vessels Nikopol and Berdyansk, and the military tug Yani Kapu, in the Kerch Strait" before "illegally" detaining Ukrainian sailors and the three vessels.
According to the statement, the tanker, which has since changed its name to Nika Spirit, was seized by Ukrainian authorities after it arrived under the Russian flag at the Ukrainian port city of Izmayil on the Danube River on July 24.
WATCH: An official Ukrainian video handout shows members of the Security Service of Ukraine (SBU) boarding the Russian tanker.
When contacted by RFE/RL, Olena Hitlyanska, a spokeswoman for the SBU, said she could not yet share information about the sailors on board the ship.
A source told Russia’s Interfax news agency that the crew aboard the tanker is comprised of approximately 15 Russian citizens.
Russia's human-rights commissioner, Tatyana Moskalkova, said that the crew was released without being charged and that they will travel to Moscow via Moldova. Denis Golenko, the press attache at the Russian Embassy in Kyiv, confirmed their release to Interfax.
Russia’s Foreign Ministry said it was currently investigating the incident and warned Kyiv of a harsh response.
“If we are talking about taking Russians hostage, this would be qualified as a flagrant violation of international law and consequences will come quickly,” it said in a statement carried by state media.
The incident follows negotiations over the release of the Ukrainian sailors that have gained momentum.
Ukraine’s human-rights commissioner, Lyudmyla Denisova, told the Hromadske TV channel that “agreements have already been reached on returning the sailors.”
A UN maritime tribunal on May 25 ruled that Russia must “immediately” release the 24 Ukrainian sailors and three Ukrainian naval vessels that were captured.
On November 25, Russian forces fired on, boarded, and seized the three Ukrainian naval vessels near the Kerch Strait. Russia has been holding 24 Ukrainian sailors, who face up to six years in prison if convicted, since then.
Moscow claims the Ukrainian vessels illegally entered Russian territorial waters near Crimea, the Ukrainian peninsula that Russia now occupies after seizing it in 2014.
The Kerch Strait is the sole passage from the Black Sea to the Sea of Azov. It runs between Russia and Crimea, the Ukrainian peninsula that Russia took over by force in March 2014 after sending in troops and staging a referendum deemed illegitimate by Kyiv, the United States, and a total of at least 100 countries.
Russia moved swiftly to seize control over Crimea after Moscow-friendly Ukrainian President Viktor Yanukovych was pushed from power by the pro-European Maidan protest movement in February 2014.
Russia has also fomented unrest and backed separatists in eastern Ukraine, where more than 13,000 people have been killed in the ensuing conflict since April 2014.