(Fixes typo in headline)
*
Russian-backed separatist hail votes
*
Votes start in Russian-controlled Ukraine
*
Putin warns West over nuclear might of Russia
LONDON, Sept 23 (Reuters) - Voting began on Friday in four Ukrainian regions mostly held by Russian forces, the start of a plan by President Vladimir Putin annex a big chunk of Ukraine in what the West says is violation of international law that significantly escalates the war.
After nearly seven months of war that has killed tens of thousands and left some eastern cities of Ukraine wastelands, Putin signalled he will annex the regions if the people in the Russian-controlled areas vote to join Russia.
The voting, which the West and Ukraine says is a sham conducted under military occupation, began on Friday and will end on Tuesday, with results expected soon afterwards.
Voting is taking place in self-styled Donetsk (DPR) and the Luhansk People's Republics (LPR), which Putin recognised as independent just before the invasion, and Russian-controlled areas of the Kherson and Zaporizhzhia regions
"All of us have been waiting for a referendum on joining Russia for 8 long years," said Leonid Pasechnik, the Russian-backed leader of Luhansk. "We have already become part of Russia. There remains only a small matter – to win (the war)."
"We are returning home," said the Russian-backed leader of Donetsk, Denis Pushilin. "Donbas is Russia."
Outcomes that support joining Russia are almost certain, as is a swiftly choreographed legal annexation along the lines of the 2014 annexation of Crimea, which took just days.
As voting began, Ivan Fedorov, the deposed Ukrainian mayor of Russian-occupied Melitopol, part of Zaporizhzhia province, said on Telegram that a loud explosion was heard by residents in the city centre at 7 a.m. local time.
"People are afraid to leave their homes," Fedorov said.
Though Russia recognised Ukraine's post-Soviet borders under the 1994 Budapest Memorandum, Putin considers swathes of eastern and southern Ukraine to be Russian possessions that were lost due to mistakes by Soviet leaders Vladimir Lenin and Nikita Khrushchev.
Ukraine says it will never accept Russian control of any of its territory and will fight until the last Russian soldier is ejected.
"The Kremlin is organizing a sham referenda to try to annex parts of Ukraine," U.S. President Joe Biden told the 77th Session of the United Nations General Assembly.
"Ukraine has the same rights that belong to every sovereign nation. We will stand in solidarity with Ukraine," said Biden, who cast the war as part of a global contest between democracy and autocracy.