Ukraine says more than 16,000 Russian troops have now been killed in Vladimir Putin's invasion.
It comes as Ukrainian soldiers push back towards Kherson in a bid to retake the captured city.
The Kremlin is suffering crippling losses in the conflict, with many of its top commanders now dead.
Morale among the rank and file of Russia's army is also said to be low as Russian forces are pushed back.
Putin has finally admitted that 1,351 soldiers have been killed in the invasion, with 3,825 wounded, although the real figure is likely far higher.
The General Staff of the Armed Forces of Ukraine claims that 16,400 Russian soldiers have been killed so far.
It also said the Kremlin had lost a huge amount of equipment, including 575 tanks, 1,640 armoured vehicles, 117 planes, 127 helicopters and seven ships.
Ukrainian president Volodymyr Zelensky echoed the claim that more than 16,000 Russian troops had been killed in the conflict during his night-time address.
He said his soldiers had delivered 'powerful blows' to Moscow and called for Putin to negotiate, but warned he would not give up sovereign territory.
Meanwhile, NATO also estimates that between 7,000 and 15,000 Russian soldiers have died in the invasion.
Ukraine is now said to be on the brink of recapturing Kherson in the country's east - the first major city to fall to the Russians.
An adviser to the Ukrainian ministry of defence, Markian Lubkivskyi, predicted troops could take the city back on Saturday.
Mr Lubkivskyi told BBC Radio 4's Today programme: "I believe that today the city will be fully under the control of Ukrainian armed forces.
"We have finished in the last two days the operation in the Kyiv region so other armed forces are now focused on the southern part trying to get free Kherson and some other Ukrainian cities."
Facing unexpectedly fierce resistance, the Russian defence ministry said that having accomplished the "first phase" of military operations, its forces would concentrate on the Donbas region part-held by Moscow-backed separatist rebels.
Western officials said the Russian statement was a recognition its forces were overstretched and may have to "pause" operations around Kyiv and other cities while they focus on the east of the country.
"It is clear that Russia is recognising that it can't pursue its operations on multiple axes simultaneously," one official said.
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"Therefore it is having to concentrate its force, particularly its logistics supply and its firepower, on a more limited number of approaches."
In the besieged city of Mariupol, authorities said about 300 people died in a Russian air strike earlier this month on a theatre where hundreds of people were sheltering.
If confirmed, it is likely to lead to renewed calls for Western powers to step up military support for the Ukrainian forces.
