Tensions have spiralled between the two countries after Prague accused Russian military intelligence of being behind a deadly 2014 explosion at an ammunition depot and expelled 18 Russian embassy staff.

Russia retaliated by ordering out 20 Czech diplomats -- sparking an angry ultimatum from Prague for Moscow to let them return or face further expulsions from its embassy.

The Czech foreign minister briefed fellow NATO members on Thursday that Prague had pinned the blast on two Russian agents suspected of also carrying out the 2018 Novichok nerve agent poisoning of former spy Sergei Skripal in Britain.

"In response to its determination of Russia's responsibility for these actions, the Czech Republic has expelled 18 Russian officials who are members of Russia's intelligence services, and is considering further substantial measures," a NATO statement said.

"Allies express deep concern over the destabilising actions Russia continues to carry out across the Euro-Atlantic area, including on Alliance territory, and stand in full solidarity with the Czech Republic," it said.

Prague on Tuesday called on fellow EU and NATO countries to expel Russian diplomats in a coordinated show of support similar to one that happened with Britain after the attack on Skripal.

Allies in the two blocs have however so far shied away from taking joint punitive measures against Moscow at a time of rising tensions with the Kremlin over its troop buildup on the border with Ukraine and the health of Russian opposition leader Alexei Navalny.