Mariupol, Ukraine

Pro-Russia activists celebrate on a Ukrainian tank abandoned in the eastern Ukrainian city of Mariupol by the Ukrainian army the day before because of engine trouble. (Fabio Bucciarelli / AFP/Getty Images / May 10, 2014)

As violent clashes flared anew in eastern Ukraine, pro-Russia separatists summoned their supporters to vote Sunday on whether to seek autonomy from the government in Kiev despite widespread condemnation of the rogue referendum and retracted support from the Kremlin.

Ukraine's interim president, Oleksandr Turchynov, warned residents of the volatile Donetsk and Luhansk regions, where armed militants occupy key government buildings, that the vote was "a step into the abyss for the regions."

Those pushing for the Russian-speaking eastern and southern areas to split from Ukraine "don't understand that this would be a complete destruction of the economy, social programs and general life for the majority of the population," Turchynov warned Saturday in a statement on the presidential website.

Donetsk, a regional capital with a population of about 1 million and the epicenter of the militants' campaign for independence, was quiet late Saturday and strangely devoid of pedestrians in the central city. Many people who oppose joining Russia were keeping their distance from the referendum and its armed and masked proponents, some residents said.

The eve of the referendum brought a second day of fierce fighting between separatists and supporters of the Kiev government in Mariupol, Russian and Ukrainian news agencies reported. At least seven people were killed Friday in a shootout over control of the city's police headquarters on the main road from the Russian mainland to Crimea, the Ukrainian peninsula seized and annexed by Russia in March. The police headquarters was set ablaze and destroyed, news reports said.

The fighting Saturday between Ukrainian government forces trying to retain control of the Mariupol government and the armed separatists focused on an army installation, where exchanges of gunfire were reported in the afternoon. Looting was also reported at shops in the city of about 500,000 on the Sea of Azov, northeast of Crimea.

Unlike in Crimea, Russians are a minority in the rest of Ukraine, where recent polls showed a solid majority against secession and alignment with Russia even in the eastern areas.

Reports in Kremlin-controlled Russian media describe the militants as "protesters" demanding a national dialogue aimed at transforming Ukraine into a loose federation in which regions would determine their own economic and foreign policies. That would allow the Russian-speaking areas with traditional ties to Moscow to opt out of the Ukraine central government's plan to bolster trade and relations with the European Union, a westward shift in political alliance that the Kremlin opposes.

Whether Sunday's referendum proves more than an unrecognized and unmeasurable expression of the separatists' desire to align with Russia depends much on Russian President Vladimir Putin. He is accused by Kiev authorities and their Western allies of fomenting the unrest in the east to destabilize Ukraine and put in doubt the legitimacy of its May 25 presidential election.

Putin called on the separatists last week to postpone the referendum, bowing to a request by the Organization for Security and Cooperation in Europe for more time to work out a diplomatic solution to the conflict over eastern Ukraine's future.

The self-proclaimed leader of the "People's Republic of Donetsk," Denis Pushilin, rejected Putin's advice, claiming local advocates of separation from Kiev have demanded the opportunity to vote now.

Putin may have signaled the limits of his support for the separatists with his request for a delay of the referendum. Kremlin instigation of a similar vote in Crimea and its widely condemned annexation of the peninsula led to the United States and European Union imposing sanctions on Russian officials and Kremlin-allied businesses. Though limited, the sanctions and the threat of more have scared away foreign investors and caused double-digit percentage drops in the value of Russian stocks and the ruble.

Putin showed little sign of backing down from his defiant posture as defender of Russian people and interests in neighboring countries during Victory Day displays of Russian firepower on Friday, including his first visit to Crimea since the territory was annexed. But he has said little about the Donetsk and Luhansk referendum since his unsuccessful call for its delay, leaving him seemingly unobliged to recognize its result or to respond to any appeal for Crimea-like annexation.

There will be no international monitoring of the referendum Sunday, probably leaving the legitimacy of the vote count open to criticism and speculation of fraud.

Surveys across Ukraine by local and international pollsters suggest that the majority in the two regions is unlikely to back secession. Surveys last month by the Donetsk-based Institute for Social Research and Political Analysis and the Washington-based Pew Research Center and International Republican Institute all showed a large majority of those in the east and south favoring a unified Ukraine.

In the Donetsk survey, only 16% of residents questioned said they supported the armed occupation of government buildings. A Gallup poll conducted for the International Republican Institute found just 4% in favor of breaking away from Ukraine to join Russia.

Efforts to distance the Kremlin from the uphill political battle of the Ukrainian separatists may also have been signaled by a rhetorical shift in Russian state-controlled media in recent days. Influential news services like Itar-Tass that have consistently labeled Turchynov and acting Prime Minister Arseny Yatsenyuk as nationalists and "coup-installed" suddenly changed their descriptions of the interim leaders Thursday to "parliament-appointed."

Turchynov and Yatsenyuk were named to run the country in late February, when the elected president and Kremlin ally, Viktor Yanukovich, fled the country after being toppled by a pro-Europe rebellion. Yanukovich's Party of Regions had controlled the national parliament, but many of the deputies defected to the opposition during the three-month revolt or fled the capital after he did. The Kremlin has consistently referred to the remaining parliament's appointments of interim leaders as the results of a coup d'etat.

Whatever the reported outcome of the referendum, Putin is under little pressure to act on the results, having urged the proponents to postpone the vote. And should majority support for independence from Kiev be expressed — or at least reported by the unsupervised organizers — the vote could fuel further challenges to the Ukrainian interim government's authority in broader areas of the south and east, validating the Kremlin line that Russians in Ukraine are fearful about their future.

The Obama administration and European leaders have warned Moscow and the separatists against any attempts to undermine the presidential vote, which Kiev authorities hope will resolve lingering questions about their legitimacy.

But if Donetsk, Luhansk and other divided areas of Ukraine defy the national presidential polling with separatist ballots, the Kremlin and its Ukrainian supporters could cast doubt on the validity of the presidential election that, like the referendum, would fail to measure the will of all Ukrainian voters.