Russia on Sunday warned Ukraine's neighbours including NATO member Romania against hosting Kyiv's military aircraft, saying they could end up being involved in an armed conflict.
"We know for sure that Ukrainian combat aircraft have flown to Romania and other neighbouring countries," defence ministry spokesman Igor Konashenkov said in a video briefing.
"The use of the airfield network of these countries for basing Ukrainian military aviation with the subsequent use of force against Russia's army can be regarded as the involvement of these states in an armed conflict," he added.
Konashenkov also claimed that "practically all" Ukraine's combat-ready aircraft had been destroyed.
Ukrainian President Volodymyr Zelensky has repeatedly demanded that Western powers enforce a no-fly zone over Ukraine to prevent more Russian attacks.
Russian President Vladimir Putin has warned that Moscow will consider any country imposing a no-fly zone over Ukraine to have entered into the military conflict.