Expert Mark Galeotti told Newsweek that both sides in the Russia-Ukraine war have been boosting their efforts "to gather whatever information they can."

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