The Federal Security Service (FSB) said its public relations center announced the detention, claiming the man was held in the Sebezhsky District of the Pskov Region, an area bordering Belarus and Latvia. The FSB did not specify where the detainee crossed the Russian border.
In its statement, the FSB said the Swedish citizen "under the legend of joining the ranks of the Armed Forces of Russia was traveling to the Russian Federation to commit sabotage and terrorist acts at military facilities." The detainee's name was not given.
According to the security service, from February to June he served under contract in the Ukrainian army in the 24th Separate Assault Battalion as a squad commander of unmanned aerial systems. The FSB claims it has documents confirming his participation in combat operations on the side of the Ukrainian Armed Forces.
A criminal case was opened against the detainee for illegal crossing of the Russian border. The FSB also said it is deciding whether to open cases on organizing the activities of a terrorist organization and on mercenarism. The battalion in which the man allegedly served has been designated a terrorist organization in Russia.
Two days earlier, the FSB reported the detention in Yuzhno-Sakhalinsk of a Japanese citizen, Hokkaido Shimbun correspondent Imai Yuki. The security service claimed the journalist was gathering data on the number of mobilized personnel and volunteers from the Kuril Islands on orders from Japanese intelligence.