Kremlin-backed officials in Ukraine appealed to President Vladimir Putin Wednesday to annex the regions under their control, after the territories held votes denounced by Kyiv and the West as a "sham".
Ukraine called on the EU to hit Russia with more sanctions and NATO to send more weapons to the frontline after the Kremlin-installed officials rolled out the alleged results late Tuesday.
The appeal came despite repeated warnings from Moscow that it could use its nuclear arsenal to defend the territories from a Ukrainian counter-offensive that has wrested back swathes of territory this month already.
The EU slammed the "illegal" vote and said results were "falsified", while Chancellor Olaf Scholz said Germany would "never recognise the results of the sham referendums".
Lugansk was the first Russian-controlled region of Ukraine to appeal to Putin to intervene, with recently captured southern regions of Zaporizhzhia and Kherson filling in shortly after.
"Our residents made a historic choice and have decided to become part of the multinational population of the Russian Federation," the Kremlin-installed leader in Kherson, Vladimir Saldo, said in a statement published on social media.
Only Donetsk -- which along with Lugansk make up the industrial Donbas region and have been partially controlled by pro-Kremlin separatists since 2014 -- had yet to formally ask Putin for annexation.
The appeal to Putin represents a turning point in the seven-month invasion as Russian officials in Moscow suggest they could use nuclear weapons in Ukraine and Putin calls up thousands of Russian military draftees to cement the Kremlin's authority in the territories.
- 'What have we ended up with?' -
Taken together, the four territories -- Kherson and Zaporizhzhia in the south; Donetsk and Lugansk in the east -- create a crucial land corridor between Russia and the Crimean peninsula, annexed by Moscow in 2014.
Together, all five make up around 20 percent of Ukraine, whose forces in recent weeks have been clawing back ground.
Despite those gains -- particularly in the north east -- Russian forces have battered the second-largest city of Kharkiv and overnight a salvo of missiles hit a railway yard, knocking out power to more than 18,000 households.
Iryna Mayor, 51, a machine operator in the rail wagon workshop, paused from shifting rubble and laying damp and torn record books out to dry, to angrily mock the invasion.
"We're Russian-speaking people, and what have we ended up with? Have we got peace, brotherhood? No, you can see what we got," she declared, pointing at the twisted debris surrounding the missile craters.
Lawmakers are expected to vote hastily to annex the territories now that the results have been announced, and Russian news agencies have said Putin could sign legislation formalising the land grab this week.
The EU slammed the "illegal" annexation votes and their "falsified" results, the bloc's foreign policy chief Josep Borrell said and Scholz repeated that Germany believes the ballots carry no weight.
"Germany will never recognise the results of the sham referendums" in the regions of Donetsk, Lugansk, Kherson and Zaporizhzhia, Scholz told Ukrainian President Volodymyr Zelensky, according to the chancellor's spokesman Steffen Hebestreit.
- 'I'm in shock' -
Putin's threat to use nuclear weapons in Ukraine coincided with his decision to call up hundreds of thousands of military reservists to back up Russia's struggling forces in eastern Ukraine.
The move has sparked panic, protests and an exodus among military-aged Russian men for neighbouring countries like Georgia and Kazakhstan.
Moscow announced Wednesday it would no longer issue passports to Russian men called up to serve and a region bordering Russia closed to passenger cars, with both moves fuelling fears in Russia that borders could close entirely.
But at a military recruitment office in Saint Petersburg there was confusion and resignation, as draftees and their families bid each other goodbye.
Nikita, a 25-year-old reservist, had tears in his eyes as he held hands with his 22-year-old fiance as he said goodbye.
"If you have to go, you have to," he said.
"I don't know what to say. I am in shock," Alina said, her gaze locked on Nikita.
Along the frontline of Ukraine, six people were injured in the Kharkiv region by Russian strikes, officials in Kyiv said, while five civilians were killed and 10 more wounded by Moscow's forces.