Polish Prime Minister Mateusz Morawiecki and German Chancellor Angela Merkel met in Warsaw Monday and called for a firm EU response to the poisoning of a Russian former spy in Britain.

London has claimed that Russia was behind the March 4 attack on Sergei Skripal and his daughter Yulia in the English city of Salisbury — accusations the Kremlin has rejected as nonsense.

“The Russian aggressor needs to know that it can’t allow itself to attack a NATO member,” Morawiecki told reporters alongside Merkel during her visit to the Polish capital after securing her fourth term as Germany’s leader.

“We (Merkel and I) agreed to say that the European Union needs to provide a firm response, and not just a symbolic one, and we expect the topic of the Russian attack to figure among the European Council’s summit conclusions” this week, Morawiecki added.

Just like the nearby Baltic countries, Poland has been spooked by Russia’s frequent military exercises near the region and its 2014 annexation of Crimea from Ukraine.

Merkel struck a more nuanced note by expressing solidarity with London but refraining from attributing direct responsibility for the poisoning to Moscow.

“Serious information suggests that Russia has something to do with this (the poisoning). It’s now up to Russia to prove that that’s not the case,” Merkel said in Warsaw.