A drone strike on a train near the Ukraine-Poland border is a calculated escalation by Russia’s President Vladimir Putin to instill fear in Europe, German Defense Minister Boris Pistorius said on Monday.

“It is all the more important that we remain level-headed, that we do not allow ourselves to be provoked, but that at the same time we leave no doubt that we are capable of defending ourselves and will not back down if the situation escalates,” Pistorius told reporters in the northeastern German town of Wolgast.

“What Vladimir Putin is doing is dangerous. He knows that, and that is why he is doing it.”

A Russian drone hit a passenger train on Ukraine’s border with NATO member Poland on Sunday, shortly after the presence of a diplomatic train with former British Prime ‌Minister Boris Johnson and European diplomats on board.

(Reporting by Reuters TV, writing by Sabine Siebold; editing by Matthias Williams)