The charges against the spy ring, which was dismantled in March, were announced by the office of the intelligence service coordinator Mariusz Kaminski.

"Charges have been filed against 16 foreigners accused of conducting espionage activities on behalf of Russian intelligence services on Polish territory and participating in an organised criminal group," it said in a statement.

"Their assigned tasks included identifying military facilities and critical infrastructure, monitoring and documenting trains transporting military and humanitarian aid to Ukraine and preparing for train derailments," it added.

The office said all of the accused had confessed to committing the acts, which also included engaging in propaganda with the goal of turning Polish sentiment against neighbouring Ukraine.

Justice Minister Zbigniew Ziobro said on X, formerly Twitter, that each of the accused faces up to 10 years in prison.

Poland has been one of the major donors of military equipment to Ukraine and served as a transport hub for arms coming from its Western allies.