The Russian-installed administrators of Ukraine's Luhansk and Kherson regions have formally asked President Vladimir Putin to incorporate them into Russia, following hastily organised referendums that Ukraine and the West denounced as illegitimate.
Russian-installed officials in four occupied regions of Ukraine reported huge majorities in favour of joining Russia.
Western countries said the votes were a coercive exercise to provide a pretext for Russia to annex around 15% of Ukrainian territory, and threatened new sanctions against Moscow if annexation plans went ahead.
Vote tallies from complete results on Tuesday in the four provinces ranged from 87% to 99.2% in favour of joining Russia, according to officials.
In a letter published on his Telegram account, Vladimir Saldo - the Russian-installed head of Ukraine's Kherson region - said residents had made "a historic choice" in favour of Russia.
If Russia declares the four Ukrainian regions part of its territory, Putin could portray any Ukrainian attempt to recapture them as an attack on Russia itself, justifying a potentially harsher military response.
Russia says it intervened in Ukraine in part to protect Russian-speakers living in the eastern Donbas region, comprising the Donetsk and Luhansk provinces, from persecution.
Kyiv and the West reject this as a baseless pretext for a wider war of aggression.
