Russian President Vladimir Putin has illegally annexed four Ukrainian regions and vowed to use "all the power and all the means" at his disposal to defend them.
"This is the will of millions of people," he said in a speech before hundreds of dignitaries in the St George's Hall of the Kremlin.
The ceremony took place three days after the completion of hastily staged referendums in which Moscow's proxies in the occupied regions claimed majorities of up to 99% in favour of joining Russia.
Ukraine and Western governments described those votes as bogus, illegitimate and conducted at gunpoint.
In response, Ukraine's president Volodymyr Zelenski has signed Ukraine's application for 'accelerated accession to NATO'. He said Ukraine was de facto part of NATO alliance but was now looking to urgently make his country's membership in accordance with law.
“Today, Ukraine is applying to make it de jure… We are taking our decisive step by signing Ukraine's application for accelerated accession to NATO," he said.
Zelenski's defiant move came after Putin earlier today declared that Russia had four new regions.
He said: "Referendums have taken place ... their results are well-known."
"People have made their choice ... This is an inalienable right, which is enshrined in Article 1 of the U.N. Charter. People living in Luhansk, Donetsk, Kherson region and Zaporizhzhia region are becoming our compatriots forever."
Putin also planned extensive celebrations including a concert in Moscow’s Red Square, which was televised live.
He told invited spectators watching a televised patriotic pop concert on Moscow's Red Square on Friday that Russia would achieve victory in its seven-month-old military campaign with Ukraine.
Flanked by the leaders of their Russian-backed administrations, with the multicoloured spires of the 16th-century St Basil's Cathedral as the backdrop, Putin said people in the regions had made a choice to rejoin their "historic motherland". He said Russia would do everything to support them, boost their security and rebuild their economies.
"Welcome home!" he said, prompting chants of "Russia! Russia!" from the flag-waving crowd in the vast square.
The event is echoed the pomp seen after the annexation of Crimea eight years ago.
Putin was seen on stage singing along with a large crowd, as the event aimed at rousing support for men called to fight against Ukraine - as thousands of wives, mothers, daughters and loved ones slam his partial mobilisation.
The tyrant performed a bizarre gesture as he walked out on stage to formally announce the illegal annexation. He was greeted by four officials, each representing one of the territories, and tried to shake all eight hands at once.
The diminutive despot looks tiny compared to the four towering chiefs of Donetsk, Luhansk, Zaporozhye and Kherson as they all put their hands in a stack like a sports team.
The ritual is particularly bizarre when compared to Putin's previous appearances, where he would purposefully host dignitaries from either side of a comically large table.
In his speech, the warmonger claimed the peoples of Donetsk, Luhansk, Kherson and Zaporizhzhia had decided to join the Russian Federation.
He then turned on the West, claiming that countries "continue to look for new chances to weaken and destroy Russia."
"After the collapse of the USSR, the West decided that the world would forever have to put up with its dictates...
"The West expected that Russia would not be able to cope with such dictates and fall apart ... but Russia has been reborn and strengthened," he said as he aired a host of grievances against Western powers.
He said the United States and its allies waged a "hybrid war" against Russia and the separatist administrations it backed in eastern Ukraine.
He said the West had broken its promises to Russia and had no moral right to talk about democracy, and that the countries of the West were acting as the imperialist states that they had "always been".
Russia's culture and development is a threat to western nations, he added as he claimed treaties had been broken.
Amid fears of rising nuclear tensions, the dictator claimed the US had created a "precedent" by dropping two nuclear warheads on Japan at the end of World War II.
Fears of nuclear war have grown since Putin said last week he was "not bluffing" when he said Russia was prepared to use nuclear weapons to defend its territory.
Today he said Russia would use "all the power and all the means" at its disposal to defend its new lands from attacks by the West or Ukraine.
U.N. chief Antonio Guterres called the annexation a "dangerous escalation" that would jeopardise prospects for peace.
"It can still be stopped. But to stop it we have to stop that person in Russia who wants war more than life.
"Your lives, citizens of Russia," Ukrainian President Volodymyr Zelenskiy said in a Thursday evening address.
The four regions cover some 90,000 square km, or about 15% of Ukraine's total area - about the size of Hungary or Portugal.
Russian government officials have said that the four regions will fall under Moscow's nuclear umbrella once they have been formally incorporated into Russia. Putin has said he could use nuclear weapons to defend Russian territory if necessary.
Ukraine has said it will seek to take back its territory.
"Referendums have no legal value, under international law the regions are and remain territories of Ukraine and Ukraine is ready to do anything to take them back," Mikhailo Podolyak, Zelenskiy's adviser, told Italian La Repubblica.
"They were sham votes, in which few people participated. To those who went to vote they pointed their rifles in their faces ordering, 'Vote!'."
Zelenskiy promised a strong response to the annexations and summoned his defence and security chiefs for an emergency meeting on Friday where "fundamental decisions" will be taken, an official said.
On the eve of the annexation ceremony in the Georgievsky Hall of the Great Kremlin Palace and a concert in Red Square, Putin said that "all mistakes" made in a call-up announced last week should be corrected, his first public acknowledgment that it had not gone smoothly.
Thousands of men have fled from Russia to avoid a draft that was billed as enlisting those with military experience and required specialities but has often appeared oblivious to individuals' service record, health, student status or even age.
At Friday's event, Putin gave a speech, meet leaders of the self-styled Russian-backed Donetsk People's Republic and Luhansk People's Republic as well as the Russian-installed leaders of the parts of Kherson and Zaporizhzhia that Russian forces occupy.
Kremlin spokesman Dmitry Peskov did not say whether Putin would attend the concert, as he did a similar event in 2014 after Russia proclaimed it had annexed Ukraine's Crimea region.
A stage has been set up in the Moscow square with giant video screens and billboards proclaiming the four areas part of Russia.
U.S. President Joe Biden said the United States would never recognise Russia's claims on Ukraine's territory, denouncing the referendums.
"The results were manufactured in Moscow," Biden said at a conference of Pacific Island leaders on Thursday.
Turkish President Tayyip Erdogan pressed Putin in a call to take steps to reduce tensions in Ukraine.
U.N. Secretary General Guterres told reporters: "Any decision to proceed with the annexation ... would have no legal value and deserves to be condemned."
The United States and the European Union are set to impose additional sanctions on Russia over the annexation, and even some of Russia's close traditional allies, such as Serbia and Kazakhstan, say they will not recognise the take over.
What Russia is billing as a celebration comes after it has faced its worst setbacks of the seven-month-old war, with its forces routed in Ukraine's northeast Kharkiv region.
Heavy fighting continues in the four disputed regions.
Russian forces launched a rocket attack on a humanitarian convoy on the road out of Zaporizhzhia and there were dead and wounded, said Oleksandar Starukh, the governor of the region.
Starukh said people were queuing to bring aid to relatives in Russian-controlled territory and pick up their relatives when the attack occurred. He did not specify the location.
Reuters could not verify battlefield reports.
Some military experts say Kyiv is poised to deliver another major defeat, gradually encircling the town of Lyman, Russia's main remaining bastion in the northern part of Donetsk province.
Its capture would open the way into the Luhansk region.
In the past 24 hours, Ukraine's military said it had killed 43 Russian servicemen and destroyed two Russian Su-25 aircraft, four tanks, four large-calibre howitzers, two self-propelled cannons and one reconnaissance drone.
The UK Prime Minister, Liz Truss, said: “Vladimir Putin has, once again, acted in violation of international law with clear disregard for the lives of the Ukrainian people he claims to represent.
“The UK will never ignore the sovereign will of those people and we will never accept the regions of Donetsk, Luhansk, Kherson and Zaporizhzhia as anything other than Ukrainian territory.
“Putin cannot be allowed to alter international borders using brute force. We will ensure he loses this illegal war.”
