The Ukrainian Security Service (SBU) has detained a member of Russia's governing United Russia party while he was crossing the administrative border with Crimea on suspicion of infringing on the territorial integrity of Ukraine.

The SBU said in a statement that its counterintelligence unit learned that Ihor Kucheryaviy, who is a member of United Russia’s regional department in the Crimean port city of Sevastopol, had plans on December 4 to visit mainland Ukraine and apply for a Ukrainian passport.

He allegedly was an avid supporter of Russia's annexation of Crimea in 2014 and was involved in erecting roadblocks in Sevastopol during the Ukrainian peninsula's invasion.

Kucheryaviy was also allegedly awarded a medal from the Russian Defense Ministry "for the return of the Crimea" and an anniversary badge of the Russian Federal Security Service (FSB) that reads, "Veterans of the Russian special services to the defenders of Crimea and Sevastopol."

Russia's Black Sea fleet is based in Sevastopol.

In April 2014, Russian President Vladimir Putin renounced contracts that were in place with Ukraine to lease facilities for the fleet until 2042.

Kucheryaviy faces the charge of "encroachment on the territorial integrity and inviolability of Ukraine," which is punishable by up to three years in prison.