Mass conscription, intended to enlist 300,000 troops, begins in Russia while Ukrainian President Zelenskyy calls on Russians to resist "partial mobilisation" or "surrender" to Ukrainian army.
Moscow has begun its mandatory troop call-up to try to bolster a stumbling offensive effort in Ukraine, with authorities saying thousands had volunteered even as Ukraine's president urged reservists to "protest, run away, or surrender" to the Ukrainian army.
Amateur footage posted on social media since President Vladimir Putin ordered the mobilisation of reservists on Wednesday purported to show hundreds of Russian citizens across the country responding to the military summons.
The Russian military said on Thursday that at least 10,000 people had volunteered to fight in 24 hours since the order.
The call-up came as Moscow-held regions of Ukraine are to vote in the coming days on whether to become part of Russia in referendums that have been called an "unlawful land grab" by Kiev and its allies.
Moscow took these steps after Ukrainian forces seized back most of the northeastern Kharkiv region, which has been seen as a possible turning point in the seven-month conflict that had fallen into stalemate.
But men also rushed to leave Russia before they were made to join.
Flights out of Russia to neighbouring countries, mainly ex-Soviet republics that allow Russians visa-free entry, are nearly entirely booked and prices have skyrocketed, pointing to an exodus of Russians wanting to avoid going to fight.
Ukrainian President Volodymyr Zelenskyy called on Russians to resist Putin's partial mobilisation during his daily address.
"Protest. Fight back. Run away. Or surrender" to the Ukrainian army, he said. "You are already complicit in all these crimes, murders and torture of Ukrainians. Because you were silent. Because you are silent."
All eyes on annexation referendums
US Secretary of State Antony Blinken on Thursday demanded Putin to be held to account as he faced Russia in a Security Council session in which the United Nations catalogued abuses in Ukraine.
"We cannot — we will not — let President Putin get away with it," Blinken told the Security Council in a special session as leaders met at the United Nations.
Russian Foreign Minister Sergey Lavrov — whom Blinken has refused to meet individually since the February offensive — lashed out at Western accusations.
"There's an attempt today to impose on us a completely different narrative about Russian aggression as the origin of this tragedy," Lavrov told the Security Council.
The confrontation on the diplomatic stage escalated as Kremlin-installed officials in Ukrainian regions controlled by Moscow's forces vowed on Thursday to press ahead with annexation polls this week.
Four Russian-occupied regions of Ukraine — Donetsk and Lugansk in the east and Kherson and Zaporizhzhia in the south — announced that they would hold the votes over five days, beginning on Friday.
Vladimir Saldo, the Moscow-installed head of Kherson, which fell early into the Russian offensive, said the referendum would go ahead in his region regardless of the criticism.
"The date has been set. We have the green light. Voting begins tomorrow and nothing can prevent this," he told Russian state-run media.
"People have been waiting and they're demanding that this vote is held soon," he added.
The referendums are reminiscent of a similar ballot in 2014 that saw the Crimean Peninsula in Ukraine annexed by Russia. Western capitals said the vote was fraudulent and hit Moscow with sanctions in response.