Each aircraft carried an unusually high payload of cruise missiles, indicating that Russia has suffered significant losses to its long-range bomber fleet as a result of Ukrainian strikes, the report said.

Russia will take years to replace nuclear-capable bomber planes that were hit in Ukrainian drone strikes last weekend, according to Western military aviation experts, straining a modernisation programme that is already delayed.

Russian warplanes were damaged but not destroyed in a June 1 attack by Ukraine, and they will be restored, Russia's deputy foreign minister said.