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.

Russia denies being behind acts of sabotage. But it is suspected to have been behind other attacks on warehouses and railway networks in EU member states this year, including in Sweden and in the Czech Republic.

Ms Calow-Jaszewska said in a statement that a group of foreign intelligence saboteurs had been involved in sending parcels containing hidden explosives and dangerous materials via courier companies. The parcels then spontaneously burst into flames or blew up.

Western officials believe the fires originated in electric massage machines containing a “magnesium-based” substance.

Magnesium-based fires are hard to put out, especially on board a plane.