The declaration came after a video conference of leaders from Visegrad Group countries. The body is a regional cooperation platform that brings together Poland, the Czech Republic, Slovakia and Hungary.
Referring to a 2014 explosion at the Vrbetice ammunition depot, 330 km (205 miles) east of Prague, the three premiers condemned "another deplorable act of aggression and breach of international law committed by Russia on European soil."
'Disproportionate measures' by Russia
They said: "We denounce the disproportionate measures taken by Russia in response to the entirely justified decision of the Czech Republic to expel 18 Russian intelligence officers from its territory."
"We will not allow these [Russian] activities to divide Europe," added the statement, published by Polish Prime Minister Mateusz Morawiecki's office.
Prague earlier this month announced the expulsion of 18 Russian diplomats over suspicions that Russian military intelligence officers were involved in the blast at the Vrbetice ammunition depot seven years ago.
Moscow retaliated by ordering out 20 Czech diplomats and staff.
The Polish foreign ministry has previously voiced "full support" for the Czech decision.