He was responding to comments by Russian officials that such plants in the EU could be seen as "legitimate targets."
Article 5 of the North Atlantic Treaty says an armed attack on one or more NATO members is treated as an attack on all.
In an interview with Polish broadcaster TVP World, Kubilius said: "If Russia were to hit our factories, I would say that would be Article 5."
Separately, speaking at the European Parliament, Kubilius was asked about a recent exchange between Moscow and NATO over Kaliningrad, the Russian exclave on the Baltic Sea.
Russia has warned that if European states or NATO attempt to isolate the region, it could use its remaining military capabilities, including nuclear weapons.
Kubulius replied that Moscow was escalating its threats and also taking real action, including hybrid operations and sabotage.
He said the European Union was not afraid and that it was strengthening its defence readiness.
Europe should be ready to have a painful impact on Russian territory and the Russian state, he added, but would not say in advance how.
On Thursday, Russian President Vladimir Putin told the Valdai Discussion Club in Moscow that in the event of a direct attack on Russia, including on Kaliningrad, the question of using "all arms at the disposal of our country" would arise "inevitably and immediately."
He said there could be no certainty that weapons of mass destruction would never be used, but stressed that such a scenario must be prevented.
Putin also estimated that Ukrainian attacks on Russian refineries had cost his country 1 percent of its GDP.
He acknowledged that Kyiv had partly achieved its aims and said Moscow had responded in kind.
He added that Ukraine could not strike deep inside Russia without Western technical support, which he said amounted to direct involvement in the conflict.
(ał)
Source: PAP, tvpworld.pl