A series of parcel fires targeting courier companies in Poland, Germany and the UK were dry runs aimed at sabotaging flights to the US and Canada, Polish prosecutors say.
Katarzyna Calow-Jaszewska revealed late last month that four people had been arrested and authorities across Europe were investigating the incidents.
Western security officials have now told US media they believe the fires - which happened in July - were part of an orchestrated campaign by Russia’s military intelligence agency, the GRU.