According to Refuters, The Russian President's proclamation of Russian rule over 15% of Ukraine - the biggest annexation in Europe since World War Two - has been firmly rejected by Western countries and even many of Russia's close allies.
It comes as Russian forces in one of the four regions being annexed face being encircled by Ukrainian troops after Putin ordered a massive mobilization drive to get hundreds of thousands of Russian men to the front.
In one of the toughest anti-American speeches he has delivered in more than two decades in power, Putin signalled he was ready to continue a battle for a greater historical Russia using whatever tools he had at his disposal and slammed the West as neo-colonial and Satanist.
"Truth is on our side. Russia is with us!" Putin told his country's political elite, who had gathered in one of the Kremlin's grandest halls to watch him signing documents annexing four Ukrainian regions.
He said the United States had set a precedent when it had dropped two atomic bombs on Japan in 1945, but stopped short of issuing new nuclear warnings against Ukraine himself, something he has done more than once in recent weeks.
The ceremony culminated in the 69-year-old leader chanting "Russia Russia!" as he clasped the hands of the four Russian-backed officials he wants to run the annexed regions, which Ukraine is fighting to win back.
Putin said Russia and the four regions would defeat Ukraine together.
"People living in Luhansk, Donetsk, Kherson region and Zaporizhzhia region are becoming our compatriots forever," said Putin, referring to the four Ukrainian regions which he said Russia was annexing.
"We will defend our land with all our strength and all our means," he said, calling on "the Kyiv regime to immediately cease hostilities and return to the negotiation table".
Ukrainian President Volodymr Zelenskiy, speaking in Kyiv after Putin, said he was ready for peace talks if and when Russia got a new president and announced that Ukraine was formally applying for fast-track membership of the NATO military alliance, something Moscow fiercely opposes.
US President Joe Biden condemned what he called Russia's fraudulent attempt to annex sovereign Ukrainian territory, which he said was a flagrant violation of international law and said new US sanctions would hurt those who provided political or economic support to the annexation drive.
