DONETSK, Ukraine — Pro-Russia separatists in eastern Ukraine vowed Thursday to press ahead with a referendum on independence, defying Russian President Vladimir Putin’s surprise call for Sunday’s vote to be postponed.
Having captured government buildings across eastern Ukraine and vehemently denounced the interim government in Kiev as fascists, the leaders of the self-styled ‘‘Donetsk People’s Republic’’ argued that they would lose credibility if they canceled the vote.
‘‘Civil war has already begun,’’ Denis Pushilin, a prominent leader of the group, told a packed news conference in Donetsk. ‘‘The referendum can put a stop to it and start a political process.’’
The decision to proceed with the vote could be seen as a rebuff to Putin, whose call Wednesday for a postponement struck a more conciliatory tone than his previous statements on Ukraine.
It remained unclear what a referendum might look like, who would participate, how fair it might be, or even in how many or which cities it would be held.
But the separatists clearly felt they had little choice but to press on: canceling the vote would leave them without even a fig leaf of popular legitimacy and deflate their movement, perhaps fatally.
Ukraine’s acting prime minister, Arseniy Yatsenyuk, said Thursday that any referendum would lack legitimacy. Ukraine has said questions about the country’s future should be decided in nationwide presidential elections scheduled for May 25, not in any regional vote.
Feeding a sense that the let-up in tensions had been fleeting, Putin on Thursday led major military exercises that simulated a response to a massive attack on Russian soil, defense officials in Moscow said.
The separatists called the referendum to decide whether the Donbas region of eastern Ukraine, the nation’s industrial heartland of Donetsk and Luhansk, should declare independence. But with little coordination or trust among separatist leaders in different cities across the region, it was far from clear what a putative new republic would look like.
There was also widespread skepticism about the separatists’ ability to stage a referendum with even a minimum of credibility.
Boris Litvinov, a leader of the referendum effort, said that about 3 million ballots have already been printed and 2.7 million of them distributed.
But he said authorities in Kiev have denied the separatists access to voter rolls. Therefore, he said, the referendum would be an ‘‘open process’’ in which people would simply turn up at polling centers, show their passports, sign their names, and cast their ballots.
After two days of mixed messages from Russia, Putin’s real intentions about the referendum remained hard to read. Analysts in Moscow said he could be playing a double game, disassociating Russia from what is likely to be a deeply flawed contest while maintaining flexibility in how to respond.
In the streets of Donetsk, confusion reigned Thursday about what the vote really means, and there appeared to be agreement on only one thing: People want peace and stability to return.
Many expressed a wide range of views on the best way forward, which the yes-no question posed by the referendum will not be able to capture, and few seemed to want to become part of Russia. Indeed, polls show that most people in eastern Ukraine want the country to stay together.