Pro-Russian separatists in four Ukrainian regions have announced that they will hold referendums on joining Russia.
The separatists said on Tuesday that votes will be held between September 23 to 27 in territories they control in the eastern regions of Donetsk and Luhansk, the Kherson region in the south and the southeastern region of Zaporizhzhia.
Details on how the votes will be held and in which territories are not yet known.
Eight years ago, pro-Russian groups in Crimea held a referendum while Russian troops were deployed there.
Russian President Vladimir Putin annexed Crimea, citing the result of the vote as the basis of his decision.
Russia is believed to be under increasing pressure from Ukraine's counteroffensives.
The Ukrainian government strongly opposes the planned referendums.
The United States is warning that it will impose additional sanctions against Moscow if votes are held.