Moscow's forces are poised to capture all of Luhansk, which, along with the neighboring Donetsk Oblast, form the Donbas region of eastern Ukraine.

President Vladimir Putin warned the West on Wednesday that Russia could use nuclear weapons if it was struck with conventional missiles, and that Moscow would consider any assault on it supported by a nuclear power to be a joint attack.

The Russian president spoke in a video message as the Ukrainian air force said it had shot down drones and one missile launched by Russia