The chance of Russia launching a nuclear attack could grow once Vladimir Putin bogusly declares four Ukrainian regions Russian - and Ukraine needs to be ready, a regional governor has said.
Pavlo Kyrylenko, the governor of Donetsk region in eastern Ukraine, said resorting to the nuclear option would "plunge them (Russia) into an abyss" before Moscow even acted.
He also had a warning for the hundreds of thousands of Russian men who are being mobilised to fight on the frontline: come to Ukraine and die, be wounded or be captured - or stay in Russia and rise up against the Putin regime.
The governor spoke to Sky News on Tuesday as five days of voting in sham referendums on whether to join Russia were ending in the Russian-occupied parts of his region as well as the regions of Luhansk, Zaporizhzhia and Kherson, all in the east and the south.
The results, which will not be internationally recognised, revealed a landslide majority in favour of "yes", pre-empting formal annexation of the territories by Russia.
Mr Kyrylenko said the move would change nothing for Ukraine, which is intent upon fighting to reclaim all land captured by Russian forces.
Asked whether it would raise the risk of a Russian tactical nuclear strike, the governor said: "This possibility needs to be considered. I want to repeat myself. We need to be ready and Russia needs to understand such a step would plunge them into an abyss before they have even acted."
He said there was also the threat of chemical and other outlawed weapons of mass destruction.
Efforts have long been under way to evacuate people from front line areas to reduce exposure to such threats, the governor said.
He said Ukraine was also strengthening its defences in the Donetsk region to prevent Russian advances and also counter-attacking to retake Russian-controlled territory.
This is playing out on different fronts within the Donetsk region in two important battles.
Russia is targeting the Ukrainian-held city of Bakhmut, while Ukrainian forces are fighting to recapture the Russian-occupied city of Lyman.
The Ukrainians are exploiting the momentum from a stunning counter-offensive over the past four weeks that regained territory across the neighbouring Kharkiv region and panicked Russia into accelerating its annexation plans.
Asked whether he had a message for President Putin, Mr Kyrylenko, wearing military-style fatigues because of the war, said he did not think there was any point in sending messages to a "sick person". Instead he wanted to speak to all Russian people.
He said: "Russians have a choice: either come here to the territory of Ukraine and not return alive, come back with bits of your body missing or be imprisoned or rise up against the regime on the ground in Russia."