The 27-nation bloc is scrambling to plug its drone defences after NATO jets shot down Russian drones over Poland in September.

"Why did it take us more than two years and the trigger of the Russian provocation with drones against Poland, and also against Baltic States and Romania, to understand that we are not ready to detect Russian drones and to destroy them with cost-effective means?" Kubilius said in a speech in Vilnius.

"The Russians are learning. Are we?".

NATO has sent reinforcements to its eastern flank and is deploying more drone defences in the wake of the incident in Poland.

The EU has also said it wants to build a system of anti-drone defences -- but details remain in flux and any plan will likely take years.

Kubilius insisted that, as European nations play catch up, they must seek to include Ukraine and its battle-hardened military of some 800,000 personnel as a key part of their broader defences.

"If we do not do that, we shall make a historical mistake, which shall leave us weaker. And which shall leave Ukraine weaker," Kubilius said.

The rush to bolster EU defences comes as European intelligence agencies warn that Russian President Vladimir Putin could look to attack a NATO country in the coming years if the war in Ukraine ends.