Russia mounted an intense and sustained barrage of Kyiv overnight, with missiles and drones targeting the Ukrainian capital where there was a succession of large explosions, Reuters reporters in the city said.

Across the country, swarms of small explosive drones descended onto military bases and destroyed a large part of Russia's nuclear bomber fleet. The flying bombs were smuggled into Russia by Ukrainian intelligence services in a plot known as Operation Spiderweb.

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.