Officers from Poland’s Internal Security Agency (ABW) detained the man, a Polish citizen, as part of an investigation launched on the basis of materials provided by military counterintelligence, according to prosecutors in the western city of Poznań.
Prosecutors said the suspect faces charges of "participating in or acting on behalf of a foreign intelligence service against Poland."
The alleged activity is said to have taken place between July 2023 and April 2024.
A court declined a request for the suspect’s pre-trial detention, instead ordering non-custodial measures. The decision is not final and has been appealed by prosecutors.
Authorities said further details could not be disclosed at this stage due to the ongoing investigation.
The Territorial Defence Force said it was informed of the arrest on April 1 and that the commander of the 12th Wielkopolska Brigade immediately dismissed the soldier from service.
In a statement, the force said the man held only basic security clearance required for his position and was not involved in border protection or other sensitive security operations.
According to earlier media reports, the suspect recently attended a rally held in Warsaw by a pro-Russian and anti-Western group.
A court spokesman said "the available evidence does not currently support a high probability that the suspect acted on behalf of Russian intelligence," state news agency PAP reported, citing the Gazeta Wyborcza newspaper.
However, the court found there was a strong likelihood he may have committed offences such as declaring readiness to cooperate with a foreign intelligence service or collecting information for that purpose.
(gs)
Source: IAR, PAP, gov.pl