The suspect, named only as Wiktor Ż., has been formally charged with offering to work with Russian intelligence and passing on information about facilities critical to Poland’s defence.
Interior Ministry spokesman Jacek Dobrzyński said a regional court had ordered the man to remain in custody for three months.
If convicted, he faces at least eight years in prison and could receive a life sentence.
"The agency’s actions prevented the man from continuing activities that threatened defence infrastructure," the ABW said in a statement.
The investigation is being led by the agency’s branch in Bydgoszcz, under the supervision of national prosecutors handling organised crime and corruption cases.
Wiktor Ż. was detained and charged with espionage on June 4, officials said.
(mp/gs)
Source: ABW/X/@JacekDobrzynski