1 of 4 | A Russian flag is seen on a balcony in the Luhansk region of Ukraine on July 4. Luhansk is one of the regions that will stage a referendum on becoming part of Russia. File Photo by Russian Defense Ministry Press via EPA-EFE
All four are homes to substantial pro-Russia separatist populations -- particularly Luhansk and Donetsk, which are known collectively as the Donbas. Russia has partial support in Zaporizhzhia.
"The law on holding a referendum ... was passed unanimously," a Russian lawmaker said according to the state-run TASS news agency.
The referendums are following the same path that Russia took eight years ago when it annexed Crimea, a part of the former Soviet Union that was claimed by Ukraine between 1991 and 2014.
Ukrainian self defense volunteers stand outside the parliament building in Kyiv, Ukraine, on March 17, 2014, following a referendum on Moscow annexing Crimea. File Photo by Ivan Vakolenko/UPI
The annexation was condemned by most of the international community and is still not recognized as Russian territory by the West.
Ukrainian foreign affairs minister Dmytro Kuleba blasted the plan and accused Moscow of trying to come up with a pretext to justify expanding and escalating the war, which is in its seventh month.
"Sham 'referendums' will not change anything," Kuleba said in a tweet Tuesday. "Neither will any hybrid 'mobilization.'
"Russia has been and remains an aggressor illegally occupying parts of Ukrainian land. Ukraine has every right to liberate its territories and will keep liberating them whatever Russia has to say."
Since the fighting began, Russia has placed a special importance on the separatist-held areas in eastern Ukraine.