Russia's domestic security agency said the detained person was attempting to transfer information to Polish intelligence. Poland has denied these accusations.

Russia’s Federal Security Service (FSB) on Friday said it had arrested a Russian national, working for a state firm, who it said was planning to pass on sensitive information to Poland.

The FSB said the man was working at a “secure facility” in the central Penza region and was held for attempting to pass on information about his workplace to Polish intelligence, state news agency RIA reported.

Poland’s deputy foreign minister Andrjez Szejna poured cold water on the claims in comments carried by Polish news website Onet.