Voters have five days to have their say.
Referendums on officially becoming Russian territories have begun in the Donbass republics of Donetsk and Lugansk and the Russian-controlled parts of southern Ukraine.
The votes will take place from today until Tuesday next week. Preliminary results are expected to be released by Wednesday.
The Donetsk and Lugansk People’s Republics (DPR and LPR) broke away from Ukraine shortly after the 2014 coup in Kiev. They are predominantly Russian-speaking and share a border with Russia. Moscow recognized them as independent states in February.
Russia currently controls Ukraine’s Kherson Region, as well as large parts of Zaporozhye Region, which were seized after Moscow launched its military operation in the neighboring country on February 24.
Kiev, which considers these areas to be under illegal Russian occupation, said it will not recognize the vote. The EU has already called the referendums a “sham.”
DPR head Denis Pushilin said on Thursday night there are “worrying signs” that Kiev could launch an attack on the republic “in the nearest future.”
The vote takes place two days after Russian President Vladimir Putin ordered the partial mobilization of reservists. In a video address on Wednesday, Putin vowed to “do everything to ensure a secure environment during the referendums so that people can express their will.”